If you've been on Facebook recently, you've certainly seen something like the below screenshot:
A list of five things, ranked in order. Usually followed by several friend comments... who then post their own "Top Five".
It's simple, colorful and viral... and it's the ideal app considering the new Facebook Profile layout: once you create a Top Five list, it enters the Facebook feed and then encourages two activities: 1. commenting and discussion (simple thanks to Facebook's product) 2. creation of your own Top Five (simply thanks to the application's product)
And because the application is open-ended in it's purpose, it is appealing to anyone.
Since the last week in March, LivingSocial's Top Five app has become the fastest growing Facebook application - now reaching fifteen million active users:
Last week of March: 2,000,000 users End of March: 10,000,000 users First week of April: 14,500,000 users