In fact, Facebook makes it impossible for applications and users to gather this type of passive-browsing information. Facebook members can't know who has silently viewed their pages, photos, videos and other content they have posted.

The misperception that FanCheck could uncover this type of data led Facebook to ask Arulkumarasan to make the application's description clearer, the Facebook spokesman said.

According to Arulkumarasan, FanCheck calculates who are your biggest Facebook fans -- previously "stalkers" -- by counting the number of times they interact with your profile, by writing on your wall, posting comments, "liking" posts and so on.

"[It] then ranks friends in order of how often they interact with your profile. It does NOT measure page views, photo views or anything which doesn't involve a wall post -- so simply viewing someone's profile won't get you on the list," Arulkumarasan said.

The developer had to take FanCheck offline for several days because it became "too popular, too quickly" and he couldn't afford the bandwidth charges. "The application jumped by a million fans in two days, and my costs rose to nearly US$1,000 per day," he said.