Vine, a platform for 6 second looping videos. Right now they are mobile-only. The free app can be downloaded at the App Store.
The New York Humane Society was one of the first users. They tweeted a video of Parker the cat.
The good news is that Parker found a home as a direct result of the video. NYHS was smart enough to tweet again, the image I captured, announcing that Parker had found his new home.