[quote="alspal":2k1989ni]so if you start making a project in HTML5, you won't be able to choose a different runtime/exporter later?[/quote:2k1989ni]
You will be able to change exporters with existing projects. Going from Canvas to a WebGL exporter should be totally seamless, because WebGL supports all of Canvas' features and more, but going the other way would need some work on your project.
Someone from Mozilla responded to Microsoft's remarks today:http://shaver.off.net/diary/2011/06/17/ ... -platform/
In short, they seem to say: adding new features always exposes new components to possible attack - WebGL is nothing special, and it can be made robust against attacks over time anyway. (Also, they point out D3D support is in Silverlight so would have the same security problems in theory!)
I'm more convinced Microsoft are just reluctant to support OpenGL.