Do you want everyone to know where you are?

Well, your favorite social networking sites might be spilling the beans about your location .

A study out this week from Worcester Polytechnic Institute (WPI) shows that mobile social networks are giving data about users' physical locations to tracking sites and other social networking services. Researchers reported that all 20 sites that were studied leaked some kind of private information to third-party tracking sites.

"This initial look at mobile online social networks raises some serious concerns, but there is more work to be done," said Craig Wills, professor of computer science at WPI and co-author of the study. "The fact that third-party sites now seem to have the capacity to build a comprehensive and dynamic portrait of mobile online social network users argues for a comprehensive way to capture the entire gamut of privacy controls into a single, unified, simple, easy-to-understand framework, so that users can make informed choices about their online privacy and feel confident that they are sharing their personal, private information only with those they choose to share it with."

In the study, the researchers looked at the practices of 13 mobile online social networks, including Brightkite, Flickr, Foursquare, Gowalla and Urbanspoon. They also studied seven traditional online social networks, such as Facebook , LinkedIn, MySpace and Twitter, which allow users to access their sites using mobile devices.

FacebookThe researchers found that all 20 sites leaked some kind of private information to third-party tracking sites. In many cases, the data given out contained the user's unique social networking identifier, which could allow third-party sites to connect the records they keeps of users' browsing behavior with the their profiles on the social networking sites, the study said.

Mobile social networks track users' geographic location by tapping into the data on the mobile devices.

The study noted that only two social networks directly gave location information to the third-party tracking sites, but several use a third-party map service to show the user's location on a map. The study also reported that six different sites transmit a unique identifier to the user's mobile phone, enabling third-party sites to continue to track a user's location even as the phone is used for other applications.

The study did not say which of the 20 sites analyzed gave out users' location information.

"The combination of location information, unique identifiers of devices, and traditional leakage of other personally identifiable information all conspire against protection of users' privacy," researchers wrote in their report.

Social networking sites, such as like Facebook , have come under pressure in recent months to better protect users' private information.

Facebook, for instance, has been criticised not only for creating new tools to make it easier to share user information with third-party web sites, but also for making it too difficult to use the site's privacy controls.

The highly popular social networking site answered critics by offering new, simpler privacy controls .