StalkerCheck, I Mean FanCheck: Explosive New App Gains 5 Million Users in One Day

facebook top fanA clever new app on Facebook, called FanCheck, gained five million users on Sunday, according its creator, a company called Smile.

Why the growth? The app lets you see which of your friends spend the most time posting and commenting on your profile wall, and also lets you see who spends the most time posting on your friends’ walls. It’s a new way to monitor friendships, shall we say. The app used to be called “StalkerCheck,” the company says, until Facebook made Smile find a less menacing term.

As of today, the app has 15.1 million monthly active users. The way it works is that you give the app permission to access you and your friends’ data through Facebook’s Platform APIs, then it calculates who has spent the most time interacting with you. The result is a thumbnailed, ranked list of your friends. You can also see the same rankings for anyone you’re friends with.

I imagine this app has been making and breaking some relationships lately. Personally, I learned that my younger sister is my number one “fan!”

facebook fancheck

FanCheck accesses user data through Facebook’s Stream API, which lets apps access the “stream” of activity on users’ profiles. The official description on the app:

This application ranks your friends based on how often they interact with your Facebook wall. Interactions counted include wall posts, comments, likes, gifts and other public items posted to your wall. We do NOT count page views or private messages.

And, an important note. The app appears to be growing through a clever use of photo tagging. At the bottom of your top fans list, there’s a button that says “click here to share and tag this as a Facebook photo.” This means the app turns the rankings into a single photo, then tags it with all of your friends names so it appears on their profile walls. We’ve seen a few other apps using the same viral mechanism in the last several days.