You can report this issue to Youtube by clicking on the sending feedback link at the bottom of any youtube.com page.
No reason to report it to Youtube if Youtube works just fine in Chrome, Opera, & Firefox. Hell even Camino works fine albeit slower.
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Either go to youtube.com/html5 and opt-out of the trial, or install a converter, like "Click to Plugin" which does the conversion in house.
The vast majority of computer users in general, unlike the people here, don't know whether they're seeing FLASH or HTML5 video.
They simply want it to work. I've resorted to using Firefox on a lot of streaming sites now as Safari simply coughs up a hairball on a several.