YikYak

Yik Yak is an anonymous (Anonymity) Social Media app. It is available for iOS and Android and it allows people anonymously to create and view "Yaks" within a 10 mile radius (HyperLocal).[1] It differs from other anonymous sharing apps such as Post Secret and Whisper Text in that it is intended for sharing primarily with those in proximity to the user, potentially making it more intimate and relevant for people reading the posts.[2] All users have the ability to contribute to the stream by writing, responding, and "voting up" or "voting down" (liking or disliking) yaks. http://en.wikipedia.org/wiki/Yik_Yak

http://www.yikyakapp.com/