Link:
http://googlesystem.blogspot.com/2008/11/youtube-tests-even-higher-quality.html

The parameter is &fmt=18

&fmt=18 is old, isn't it?

I thought the "Even higher" 720p videos were &fmt=22

Wasn't this annouced a while ago too? I've tried &fmt=22 a few times, i'm sure.

Something here:
http://blogoscoped.com/forum/126077.html

YouTube is now testing a wide-screen player:
I am seeing it on this video: http://www.youtube.com/watch?v=3l94S1yDJEE

Okay found it on Google: http://foolrulez.org/blog/2008/11/youtube-widescreen-video-enabled/

Nice ;)