It seems like we went through this in the 90s with wmv/quicktime/etc. I can't recall why it failed & I'm not sure why it should be better this time around.
I see a lot of VP6 and Sorenson listed there. What we really have today is Flash/Flash/Flash. I'm curious about how much VC-1 use there is in the wild in the large Microsoft/Silverlight streaming video installations.