The makers of the mobile app Girls Around Me came under fire Monday for helping men to "stalk" unsuspecting women, but the incident also reveals how much we still have to learn about what social networks reveal about us.

The app collected data from FourSquare, showing local bars where women had checked in, and matched that with information from their Facebook profile, including photos and sometimes their dating status. The end result was that the app's users could see how many single women were in a particular nightspot, what they looked like and what their names were.

FourSquare blocked the app's use of its API, claiming it violated its privacy policies. That forced its developer, the Russian company i-Free, to pull Girls Around Me from the App Store.

But i-Free didn't hack into people's accounts to get at the information, it only used what people had made freely available on their social networking sites. The incident shows how compiling such public information can make people uncomfortable when it's done in unexpected ways.

"When you see something so out of context with what you expect, it ends up being shocking," said Jules Polonetsky, the director of the Future of Privacy Forum. "I get that when I'm out in a big crowd, I'm not secret. But it's still seems bizarre if someone scans every face in the crowd and then somehow identifies it. It seems to push beyond the appropriate context."

The problem, to some extent, resides in a culture gap between developers, who think that if information is available, they can use it to innovate in any way they see fit, and users, who don't always understand how revealing their digital information can be, privacy advocates said.

John M. Simpson, the director of Consumer Watchdog's privacy project, said even if people understand what data they're sharing on social networks, they don't expect it to be "reconfigured so they can be hit upon."

"Just because something is technologically possible is no justification for necessarily doing it," he said.

"Many, many people have no idea the amount of information that they're sharing on Facebook," Simpson said. He faulted the social network's default privacy settings. "People sometimes go on and never realize the extent to which things can be seen. I think that's a worrisome thing. I think default settings are tremendously important."

But Polonetsky was reluctant to blame the social networks. He called FourSquare's privacy settings "reasonably intuitive." As for Facebook, he said, "After lots of pushing and pulling and squeezing, they've ended up with a much more usable set of controls."

FourSquare said the Girls Around Me app violated its privacy policy by "aggregating information across venues," and declined to comment further. Facebook did not respond to a request for comment.

The challenge, said Polonetsky, is to use technology to provide new and interesting experiences for those who want them, without leaving other users feeling violated.

Meanwhile, the makers of Girls Around Me saidthey were trying "find a solution" to FourSquare having yanked their API. The app had been downloaded 70,000 times, they said.

Cameron Scott covers search, web services and privacy for The IDG News Service. Follow Cameron on Twitter at CScott_IDG.