Somebody told me that there is software you can buy or download to find out who has viewed your MySpace or Facebook profile page, or even who has TRIED to view it but gotten the "you have to be a friend" message. Is this for real?

I think it's kind of creepy that I could check somebody's profile to see if it was, say, somebody I went to high school with or just someone with the same name, and the person could tell it was me that looked. Spy vs. Spy?