And flash. Why haven't they disabled that?
"The latest FUD is Microsoft?s claim that they won?t support WebGL because it?s insecure. They might have a little more credibility if they weren?t promoting a technology, Silverlight 5, that provides the EXACT SAME FEATURES with all the same issues. They can?t have it both ways. Either it?s possible to make this tech safe or else it?s not. If it is possible to make it safe in Silverlight 5 then it?s also just as possible in WebGL. If it?s not possible to make it safe Microsoft would have to come out and say (1) They are removing GPU access from Silverlight 5. (2) They are banning Unity3D from running in IE since it also provides access to the EXACT SAME FEATURES. (3) They are banning Flash 11 from running in IE since it also provides access to the EXACT SAME FEATURES."
A lot of the issues have also already had solutions found. Even some of microsoft's own employees apparently disagree about not supporting webgl.