2009 showed us the potential and promise of HTML5 and it seems 2010 has already started delivering in a big way — starting wth YouTube. Last week, YouTube announced that users will be able to watch some of the site’s videos without a Flash plugin using the video and audio playback support included with HTML5.

Want to check it out for yourself? You can do so via YouTube’s TestTube site. To get the new player to work be sure to use Chrome, Safari, or ChromeFrame on IE. I should note that this functionality has not been rolled out all of YouTube’s videos. It seems you can only watch videos that aren’t being monetized and haven’t been annotated. Nonetheless, I’m excited to see a “mainstream” media outlet take such a big step towards moving HTML5 into the lime light.

After testing it myself I did experience one bug using Chrome for the Mac (clicking full screen crashed my browser) but the only way I could truly tell it wasn’t a Flash player was by right-clicking and not getting the “about Flash…” dialogue.

All of this got me wondering: Is Adobe freaking out by the idea of media sites no longer relying on the Flash plugin to deliver content? Are they already planning for any kind of revenue loss from multimedia developers shifting focus to doing what they do using HTML5? Probably not, but 2010 should offer many insights into what kind of impact HTML5 will have on content delivery in the long run.