As well as the picture-sharing app, the researchers created a tool for sharing location information with friends. Friends can receive a notification when a user enters an area drawn on a map (see video of the app being demonstrated). But users restrict the amount of information shared by their phone. "It's my location, so I get control," says Mohomed. "If my boss wanted to track my location, I could allow them to do it only during the week, for example."

Mohomed thinks some people will be attracted by the idea of a more secure social network, although he admits that a provider might need to find a different business model--many networks, including Facebook, rely on being able to access user data in order to deliver tailored advertising.

"I may not care that Flickr can see my photos and messages, but people may feel differently about location sharing," says Mohomed. "Imagine you are using an application that allows you to track your kid's cell phone--what if their server is compromised?"

David Koll, a researcher at the University of Göttingen, Germany, agrees that such scenarios are worth worrying about. He points out that there have been recent examples of servers being hacked. Social service provider RockYou, for example, had the login details of 32 million users stolen last year. "It's good to think about different ways to run social networks," he says. "People are becoming more aware of their privacy, and having a central store that knows everything has risks."

Koll and his Göttingen colleagues are working on an alternative social networking architecture for mobile devices of their own. It would do away with a central server altogether, and have user data in secure caches distributed across the devices in the network. Having a central server has benefits, though. A cloud-based platform is straightforward to scale, says Mohomed. "If you have more users or traffic all of a sudden, perhaps due to a natural disaster, you just add more cloud instances to handle it."