For the new report, researchers examined 20 "mobile social networks," including services like Facebook and MySpace that now allow access from mobile phones, sites like Flickr and Yelp, and mobile-specific services like Foursquare and Loopt. All 20 were found to leak some private information.
In some cases the data that was leaked was a unique identifier or user id, while in other instances the shared information was specific pieces of personal data. Several of the companies shared data about users' locations.
That mobile companies might be compromising people's privacy probably shouldn't be surprising, if for no other reason than that there appears to be demand for as much data about users as possible. Additionally, transmitting information about users doesn't appear to violate any laws -- at least not yet. Should the Boucher bill be enacted, companies would need people's consent to gather precise geolocation data.