Everyone's been bashing Flash lately and holding HTML5 up on a pedestal. This circular graph thing, for example, shows what a combination of HTML5 and CSS3 can do and what features are available in major browsers. That's great and all, but as you can see there are still a lot of holes.
The most glaringly obvious hole is Internet Explorer - which supports practically nothing. This is nothing new. Anyone who's designed a site to work in all browsers knows this. But as much as you hate Internet Explorer, you're not going to block content for some 80 percent of visitors, right?
On top of that, Flash provides richer interaction than HTML5 right now, and it's going to be like that for a while. A lot of the work from the New York Times is in Flash. Stamen Design uses Flash. A lot of great work has come out of Flash - not just cruddy MySpace pages.
Now I'm not saying HTML5 isn't going to be useful. It will be and is in some areas. But in terms of visualization, Flash is still better.