I find it interesting that everyone comments on flash/silverlight being proprietary and no one talks about H.264 which is required along with HTML 5 to replace flash. This is a proprietary standard which just happens to be owned at least partially by Apple. If you want to argue about the proprietary issues then this has to at least be discussed. I am in the market to buy my first mac in the next month or so if they come out with an i5/i7 macbook pro but I'm not impressed when I see this kind of information and am considering rethinking a purchase. As a possible future purchaser and I own about 4-5 computers which I will eventually replace and possibly my phone as well, this kind of info about Apple doesn't impress me. Still strongly considering but they will really have to impress me with their GRAPHICS options as well as their chips. No ipad for me until they give an SD card slot (expandable storage), support for the current standards, real eInk, and multitasking (which I can do with my blackberry storm, and commonly flip between web, game, messages, applications).
How is H264 proprietary? It is an "open standard" developed by the same group that has JPEG and MPEG2 (DVD anyone?), MP3 (audio anyone?). MP4 is the video file format and H264 is the best codec for it, bar none.
Now it may require the makers of players to license a decoder, as does MPEG2 for DVD, but that doesn't make it proprietary in any shape or form. Apple happens to include a hardware decoder for it in their devices, and everyone else is too cheap. It is very nice quality, clear video for its file size.
You don't need decoding software or plugins from Apple to play it. Other than update their codec support, browsers could cope with it fine, because it is MP4 and most browsers handle that out of the box -- that is how open it is, and how going HTML5 is only confirming a natural route that is already being taken. Google have shown the way with YouTube.
Flash and Silverlight are proprietary in the sense that you need the software from Adobe and MS and Adobe and MS are in full control of their development (or non-development as the case may be). So, the BBC, etc. can just got off their lame anti-Apple kicks, get out of bed with MS and stop spiting their own noses by using the truly proprietary junk that come out of Adobe and MS and for which we have to keep messing with plugins.
Thank goodness the standards bodies "saw the light" and didn't make Silverlight the de facto standard for HTML5 video, but left it open so that video can be defined by the web developer just as images are now (you can include links to JPEG, GIF, PNG, etc. and they "just work" -- without the need for different individual plugins for different types of images, or hadn't you noticed that it's something that you don't have to notice).
The idea is that now video on the web will "just work" through the browser, without proprietary plugins for various types of clips you want to watch. And BTW you don't "need" H264 video along with HTML5, but it is at this point the best option.
So, tell me, what plugins are you needing to view the H264 versions of the YouTube videos? As for Graphics, a plethora of options aren't quite as critical on the Mac as they are on a PC -- Quartz technology is pretty well sorted, while Aero, or whatever MS' attempt at copying Quartz is called, seems to be a real hit or miss area.