Someone who browses the internet scouring social network sites for pictures of people they find attractive. They will often save their profile picture to a private file on their computer and fantasize about them.
Statistically 4/5 people are unknown victims of profile stalkers!
As for the other 1/5.... well, they are the profile stalkers.
A profile stalker often sends at least 10 friend requests a day and will prey on unsuspecting victims. They ususally have about 2000-3000 so called 'friends' on Facebook.