In Silverlight 4, Microsoft has also implemented Component Object Model (COM) automation, introduced by Microsoft in 1993 as a binary-interface standard for software componentry that can be used to enable interprocess communication and dynamic object creation in a large range of programming languages. It's a feature only available on Windows. Again, this is counterintuitive for a plugin that is meant to be cross-platform, so we asked Microsoft about it. "Microsoft is committed to providing full cross-platform and cross-browser support with Silverlight and to optimizing Silverlight to light up every platform on which it runs," a Microsoft spokesperson told Ars. Well that's all nice and dandy, but the Silverlight team is breaking cross-platform support so they can support COM.

Silverlight is never going to be as popular as Flash. Period. Don't be fooled by "penetration" numbers. People don't want a Windows-only interface to a Windows-only web. This is not going to work.

Lack of cross-platform support in Silverlight 4 explained