Looks like Wikipedia is on track to become a big server of HTML5 WebM videos. The absence of H.264 support (assuming they hold on to that) might finally push Microsoft and Apple to support WebM out of the box. Maybe we will also see more hardware support for WebM in mobile devices...
I liked this example: <a href="http://commons.wikimedia.org/wiki/File:Great_Feeling.ogv" rel="nofollow">http://commons.wikimedia.org/wiki/File:Great_Feeling.ogv</a>. It also showcases the subtitles feature of the player. It didn't play the first time I tried it (current stable Chrome on Ubuntu) but reloading helped.
I would be interested in knowing the financials behind this. Video is expensive to serve and store: these costs become more noticeable if they get a lot of growth of Video uploads.As much as I love HTML5 Video , it drives up your storage and transcoding costs by two to three times if decide to support WEBM, OGG and MP4(though I see they are not doing MP4). If they are transcoding the video ,then that would add to CPU costs. Of course, I am basing my assumptions of AWS, Zencoder etc. I would love to hear how to plan to contain costs.
So, nobody cares about more widely adopted <object/> which was supposed to be a solution for future media types and just happens to usually be more stable, have better perfomance and support much more media formats without having to invent new elements for each media type. Not even as a fallback.