All of the videos on our support page are now available as Ogg Theora files. Theora is a high quality video codec that is not patent encumbered. You can read about free formats on Wikipedia. As to why you should care, read Jimmy Wales’ two year old blog post on Free Knowledge requires Free Software and Free File Formats.
Thanks to those who bugged us about making all videos available in Theora format, most recently Matt Lee, the FSF‘s webmaster, and to Alex for figuring out how to transcode the audio track from the last video we had yet to convert (answer: build
ffmpeg2theora from source with support for the needed codecs compiled in, duh!)