Responses (4)
I've seen a load of things promising this but they are lies, trying to play on people's curiosity about who is looking at them. If you want to be surreptitious about it, though, I suppose it would be possible to find out by writing a worm which checks the most common browser caches for your profile picture, records every time it finds it, and deletes it (meaning if the person comes back to your profile the picture needs to be reloaded and the worm knows that person has come back).
Ah, I was just curious about it.