The future will be (auto)captioned

YouTube has turned on the ability to add full closed captions to videos. This will not only allow videos to appeal more directly to foreign audiences, but will give YouTube excellent data for searching videos and targeting ads to them.

Quoting the official YouTube blog:

Making video easily accessible is something we're working hard to address at YouTube. One of the first steps we took was the development of a caption feature in 2008. In November of last year we released auto-captioning for a small, select group of partners. Auto-captioning combines some of the speech-to-text algorithms found in Google's Voice Search to automatically generate video captions when requested by a viewer. The video owner can also download the auto-generated captions, improve them, and upload the new version. Viewers can even choose an option to translate those captions into any one of 50 different languages -- all in just a couple of clicks.