Stalker Check is an application developed for social networking sites, specifically facebook and twitter.
This app does not actually tell you who is stalking you over the internet, for as the app originally clearly stated (this has for some reason been removed) that real stalkers (ie people who view your page/photos all the time) are protected under facebook/twitter privacy.
what this app actually does is rank people in your friends on how many of the last 200 interactions on your page (wall posts, photo comments, status comments, etc) involved each person. as a result, this app is much more like a 'top friends' app.
however, it has amassed great popularity, becoming the latest craze to sweep facebook. there is a steadily growing tendency to screenshot the stalker list, upload it as a picture, then tag everyone in it. this annoys a lot of people.
in the early stages of this app there were many problems, which have been mostly patched. however, there is still a slight discrepancy occasionally when viewing a friends stalker list.
Guy 1: Wow, that girl, (insert hot chick here) has been stalking me!
Guy 2: What gives you that impression?
Guy 1: Stalker Check!
Guy 2: If she were really stalking you, she would be protected by facebook privacy!
"Hey, you perv your my #1 stalker on Stalker Check. WTF?!"
"Yeah thats because I 'like' every message you post!"