That's really a myth though isn't it? It's weird that when you call something a standard, people then automatically credit it with being built into browsers and not needing a plugin, when in reality Flash reaches far more desktops than HTML5 does or will
even in 2 or 3 years. Even Silverlight, well behind Flash, almost certainly has more installations than browsers that have HTML5 features.
Certainly developing content that requires a plugin isn't inherently attractive, but when I see things like Apple's streaming event last week and Google's Wave that require a large percentage of their potential audience to
install a whole new browser, that's the very definition of a "boil the ocean" strategy.