Twitter handle: @youtube
Joined Twitter: Nov. 13, 2007
First tweet: August 28, 2008. "Follow Obama's nomination week at http://www.youtube.com/user/2008conventions"
Google's video service is the only brand in Twitter's Top 10, but that's not really surprising on a site so focused on mobile users. All of that video content reaches roughly 56% of the U.S. Internet audience, according to ComScore. That rivals Facebook's reach and outpaces heavy hitters such as Wikipedia, Amazon (AMZN - Get Report) and AOL (AOL).
Also, take a look at that first tweet. In four years, YouTube has become a hub for U.S. political coverage as well as the site your great aunt uses to watch her cute cat videos. When you become as important to protestors in embattled countries as you are to office workers just getting around to watching Gangam Style, that's about as close to indispensable as you can get.