"My friend got a call from her friend at Facebook, asking why she kept looking at his profile," says a privacy-conscious source at a major tech company. Turns out Facebook employees can (and do) check out anyone's profile. Not only that, but they also see which profiles a user has viewed — a major privacy violation. If you've been obsessed with a workmate or classmate, Facebook employees know. If Barack Obama's intern has been using the campaign account to troll for hotties, Facebook employees know. Within the company, it's considered a job perk, and employees check this data for fun.
The site does not allow regular users to see which profiles other users have seen. While one third-party application lets users voluntarily make their profile-visiting known, no application allows one to "spy" on the activity of an unknowing user.