wow thanks! sounds pretty goodYour Mac was just getting back at you for watching a video about the Microsoft Zune. J/K.
No really, flash sucks. I recommend ClicktoFlash. It disables flash automagically and can automatically watch youtube videos in h.264 so your CPU won't die of a heart attack.
Consider yourself lucky. In OS versions before SL, the Flash plugin would have crashed Safari completely. Now in SL it's walled off from the rest of Safari. Maybe if enough users see just how often Flash crashes, they will bang on Adobe door to write a better plugin.