The purpose of this note is to characterize the challenges entrepreneurs may face in creating a well-functioning ecosystem of users, and to equip entrepreneurs with tools to overcome these obstacles. The note is meant to accompany the final module of the "The Online Economy: Strategy and Entrepreneurship," an elective course taught at Harvard Business School. This is an abridgment of HBP 911066.

Entrepreneurs starting online businesses often need to mobilize multiple sets of users or customers, each of whom hesitates to participate unless others join also. This case presents several challenges with similar structure.

SaferTaxi, a taxi booking service in South America must develop its mobilization strategy; that is, it must attract enough passengers and drivers to make its service worthwhile for all. Drivers hesitate to pay for SaferTaxi's smartphones and service unless these will deliver passenger bookings -- and passengers have no reason to sign up unless drivers are available. Meanwhile, regulators question the permissibility of online taxi booking in light of regulatory requirements, and some existing taxi booking vendors feel threatened by SaferTaxi's efforts to enter the market. As SaferTaxi attempts to satisfy these diverse constituents, international competition looms. What should SaferTaxi's founders do next?

As Zillow's real estate search service gains user adoption, some real estate professionals question Zillow's policies, fees, and power. Dissatisfied real estate professionals could remove listings from Zillow, reducing the service's value to users. Should Zillow adjust its approach in order to address complaints?

Jon Pastor and Lawrence Zhou were inspired by the same problem: the Internet was surprisingly unhelpful in the hunt for an apartment. The online apartment rental market was fragmented, opaque, and wrought with misinformation. The leader in this space was the website Craigslist, which was the most highly trafficked classifieds site in the world and the tenth most visited site in the United States despite introducing almost no innovations in its 15 years of existence. Having suffered as consumers, Jon and Lawrence saw this chaotic space as fertile ground for entrepreneurship. But the routes these entrepreneurs chose to take were different. "Killing Craigslist" explores the business Jon and Lawrence built to improve the online rental experience, and examines strategies to attract users and monetize their sites, all in shadow of a deeply entrenched incumbent.

French advertising company JCDecaux and the city of Paris jointly developed Vélib', a wildly popular bicycle sharing system. Despite Vélib's public appeal, vandalism and theft led to ballooning operating costs-costs borne by JCDecaux alone. The two parties opted to renegotiate their contract, which would impact prices, revenue sharing, cost allocation, and the operation of the system as a whole. Could the parties agree on a common strategy that would meet their objectives, while still delivering a first class bicycle sharing service to the city of Paris?

French advertising company JCDecaux and the city of Paris jointly developed Vélib', a wildly popular bicycle sharing system. Despite Vélib's public appeal, vandalism and theft led to ballooning operating costs-costs borne by JCDecaux alone. The two parties opted to renegotiate their contract, which would impact prices, revenue sharing, cost allocation, and the operation of the system as a whole. Could the parties agree on a common strategy that would meet their objectives, while still delivering a first class bicycle sharing service to the city of Paris?

Birchbox offers trial-sized beauty products delivered monthly by mail -- attracting rave reviews. Seeing the success of this model, numerous "copycat" clones seek to offer the same service. Many of these copycats focus on non-U.S. countries, but others are challenging Birchbox on its home territory. Can Birchbox defend its position? How?

This note provides an overview of the Harvard Business School course "The Online Economy: Strategy and Entrepreneurship." It covers the framework for the course, key principles within each course module, and a synopsis of each case, along with the lessons the case is meant to convey.

"Market Design in Online Businesses" characterizes the challenges entrepreneurs may face in creating a well-functioning ecosystem of users, and helps equip entrepreneurs with tools to overcome these obstacles. Key principles include ensuring thickness, alleviating congestion stemming from overuse, addressing asymmetric information, ensuring that it is safe and straightforward for users to participate, and designing monetization strategies that do not disrupt, but instead contribute to the well-being of the ecosystem.

This module note presents six strategies for mobilizing networked businesses.

This simulation presents students the opportunity to experience firsthand the economics of carbon markets and permit trading. Each student has private role information about a company he or she manages. The student must make decisions about pollution-reducing investments and production levels in the face of uncertainty about pollution permit prices. Students form groups of five, and throughout the exercise students may buy or sell permits within their group. Trading outcomes dictate permit prices, and at the end of trading, each firm calculates profits and pays over pollution penalties as needed.

This simulation presents students the opportunity to experience firsthand the economics of carbon markets and permit trading. Each student has private role information about a company he or she manages. The student must make decisions about pollution-reducing investments and production levels in the face of uncertainty about pollution permit prices. Students form groups of five, and throughout the exercise students may buy or sell permits within their group. Trading outcomes dictate permit prices, and at the end of trading, each firm calculates profits and pays over pollution penalties as needed.

This simulation presents students the opportunity to experience firsthand the economics of carbon markets and permit trading. Each student has private role information about a company he or she manages. The student must make decisions about pollution-reducing investments and production levels in the face of uncertainty about pollution permit prices. Students form groups of five, and throughout the exercise students may buy or sell permits within their group. Trading outcomes dictate permit prices, and at the end of trading, each firm calculates profits and pays over pollution penalties as needed.

This simulation presents students the opportunity to experience firsthand the economics of carbon markets and permit trading. Each student has private role information about a company he or she manages. The student must make decisions about pollution-reducing investments and production levels in the face of uncertainty about pollution permit prices. Students form groups of five, and throughout the exercise students may buy or sell permits within their group. Trading outcomes dictate permit prices, and at the end of trading, each firm calculates profits and pays over pollution penalties as needed.

This simulation presents students the opportunity to experience firsthand the economics of carbon markets and permit trading. Each student has private role information about a company he or she manages. The student must make decisions about pollution-reducing investments and production levels in the face of uncertainty about pollution permit prices. Students form groups of five, and throughout the exercise students may buy or sell permits within their group. Trading outcomes dictate permit prices, and at the end of trading, each firm calculates profits and pays over pollution penalties as needed.

Lindsay Ronga and Gary Vaynerchuk are launching Cork'd, an online social network for wine lovers. Despite Gary's status as a celebrity wine connoisseur, the team faces a significant challenge: several other wine social networks are well established and already have large user bases. How can Cork'd gain traction in this crowded space?

Ocean Tomo's management team sought to turn the company into the leading intermediary for intellectual property. Despite its increasingly important role in the global marketplace, IP remained a notoriously illiquid asset--difficult to value, harder to trade, and often underutilized by owners. CEO Jim Malackowski and his colleagues hoped to capitalize on this inefficiency by designing and operating innovative marketplaces for intellectual property. After a successful live IP auction in the spring of 2008 (62% of 85 offered lots were sold for a total of $19.6 million), Ocean Tomo had to decide which of its five business lines to emphasize. Indeed, from its inception, Ocean Tomo had been designed as a "one-stop shop" for IP services, with five inter-related lines of business. Which of these services provided the largest market opportunity for Ocean Tomo? How should the company allocate its scarce resources (it had not sought outside funding yet) in order to get the most leverage going forward?

Despite strong appeal among job seekers and outside recruiters, TheLadders' corporate job listings seem to lag. Could raising prices help solve the problem? TheLadders considers this strategic paradox.

Cambrian House builds internet-based products and services by relying entirely on its user community for all aspects of its innovation and new product development process. Users suggest ideas for new products and services and also participate in a monthly voting process to select the best ideas. The company is now considering the deployment of a prediction market to deepen user involvement and commitment in its innovation; however, it is not sure if it is an appropriate strategy for its community.