Foursquare, created in 2009 by Dennis Crowley and Naveen Selvadurai, is a location-based social networking service for mobile device users. As of April 2012, the company reported it had 20 million registered users . The website and the mobile application allow registered users to check in the places they visit and share to their Twitter and Facebook. Also, users can save a place to a to-do list for later visiting. Foursquare introduces itself as “when you’re looking for inspiration for what to do next, we’ll give you personalized recommendations and deals based on where you, your friends, and people with your tastes have been.”  And this is the feature they want to focus on at present.
How Is It Shaped? And How Does the Structure Affect the Users’ Behaviour?
Since Foursquare is blocked in China, actually I never used it before. But I’m a loyal user of a similar Chinese mobile application. As a new user of Foursquare, I analyzed the structure of it (both the website and the mobile app) and identified the design patterns  used, as shown in the graph below:
Obviously, check-in is addictive, collecting badges is fun, and becoming the mayor of a place is a proud thing. All of these arouse the enthusiasm of users to contribute content (UGC) of Foursquare, at least, in the beginning of its appearance.
The Activity Stream shows all your friends’ latest activities. You can leave comments on any check-in, or just say you like it! This encourages users communicate with each other, as many of other social networks do.
If you have visited a place, you may write some tips of this place. The function of Tips is a kind of presentation or review of a certain place written by users. This will affect other users’ impression of the place, especially those who have never been to the place.
However, already 4 years after Foursquare was launched, there are already so many other social networks providing location-based services. You can share your location directly in Facebook instead of checking in by Foursquare and then sharing it to Facebook. This gave Foursquare a big blow and forced them to find new uses. Right now, Foursquare focusses on enhancing the Exploring Places function. This function not only shows you nearby cafes, restaurants, shopping centers, etc., but also helps you to find your next stop. As Drew Olanoff said in his blog, Foursquare wants you to dive head first into locations around you, hopefully using the app to help you decide where to go next. It is clear that the company has a ton of information and just desperately wants users to start interacting with it. 
Then, How Do They Make Money?
The functions “Special Nearby” and “Suggestions” provide users with good choices on where to go. At the same time, they allow Foursquare to benefit from its collaborators. Actually, Foursquare is planning paid services for three tiers of businesses : small, privately owned stores and restaurants; brands with retail chains, such as Tasti D-Lite; and huge multinational marketers such as Pepsi.
Especially for small stores and restaurants, Foursquare has just launched self-serve ads. If you’re searching for something (perhaps Cuban food) and a nearby business wants to get your attention, they can now pay to show up in the results. Interestingly, Foursquare says businesses will only have to pay for their ads “when people visit (in person, or the listing on Foursquare).” 
 Sarah Lacy. Foursquare Closes $50M at a $600M Valuation. TechCrunch. Retrieved 24 June 2011.
 Christian Crumlish and Erin Malone. Designing social interfaces: principles, patterns, and practices for improving the user experience. O’Reilly Media, 2009.
 Drew Olanoff. Foursquare’s Upcoming iOS Release Is A Pivotal Moment For The Company, As In It’s “Now Or Never”. 2013
 Kunur Patel. Foursquare Plots Its Business Model. 2010
 Harrison Weber. Foursquare announces self-serve ads product, rolls it out to “a few thousand” businesses. 2013