And I don't like it.
What does it mean?
It means that with the new "video" tag in html 5 the browsers become to be the player and if you have a capable system (video and graphics drivers, codecs, etc) all responsibility falls on the browsers so it would be common to see crashes on browsers, meaning the lost of caches and corruption on config data.
In my opinion, this is not a good idea.
It's good because you don't need to dig with a lot of code to embed multimedia, but, in the other hand, I find more suitable to handle multimedia with an external application via plug-ins.
Using plug-ins as flash is not a good choice, but if they develop as they should and make them as efficient as DivxWebPlayer, there is no need to use the browser as a player and lets more control in the client side, this means, the final user.
And as a side effect, we should ask... are going to let this happen common third application developers as Adobe or Real?
http://www.w3schools.com/html5/tag_video.asp
http://youtube-global.blogspot.com/2010/01/introducing-youtube-html5-supported.html