Lot of websites using theora videos already and there are already plenty of examples of sites using the new HTML5 Video tags, too
http://wiki.xiph.org/List_of_Theora_videos

x264 is the encoder, the video it produces is h264. A company called MPEG LA collects royalties but has said that internet video will be royalty free until 2015. So if they get everyone to use it, they make a killing in five years.

If you want to maintain freedom of information you have to use open standards.

Bit nasty that miro, I thought I'd give their player a shot and the installer had a 'quick' button and a 'custom' button, and only after you click the custom you really notice that it want to install yahoo toolbar and set yahoo as default search, which you then can deselect, but I expect 75% if those trying it will be fooled and get yahoodwinked.
Not a healthy business model then of that org.
Oh and it's just VLC in a nice webinterface jacket and handy link-ins to various public videos, which isn't that bad but it's not without bugs, and telling people videos are not for their area erroneously to boot.

Wikipedia had such video and audio for quite some time now, not that this cooperation might not be new, but wikipedia using the video is not.
And it shames your name that you did not know that, shows you never browse wikipedia, tisk. :)

Why not use x264?