As long as IE 6 remains the corporate browser of choice, HTML 5 will have a hard time taking off.
Consider this article:
Among the assertions:
1) As of April 30th, 2009, IE 6 represents 60% of all corporate browsers.
2) Digg tried removing support for IE 6, and found that most of its usage was by people logging in from work. A large number of them can't upgrade or install another browser since those are...