http://www.beet.tv/2009/07/video-coming-to-wikipediawill-be-viewable-on-microsoft-explorer-too.html
One of the most anticipated developments in Web video will be the implementation of open source video into Wikipedia. The recent launch of Firefox 3.5 will support the Ogg format, which will be needed to view Wikipedia videos. Explorer does not support Ogg, but watchers will be able to watch videos in a Java video player, according to Michal Tzur, co-founder and president of Kaltura.
Andy Plesser, Exec Producer