Since when has that been the case? That was true once, but today M$ diminishes value not add to it. There was a time when I was a M$ fanboy but once I started using Linux about 8 years ago I realized just how much M$ has stifled the development of the computer industry as a whole and now I have absolutely ZERO interest at running anything M$ on my tablet!!
This is honestly horrible news. Microsoft would like nothing better than to have Silverlight completely replace flash on the web. The one and only reason they're *appearing* to support other platforms than Windows is because they want to get a monopoly on Silverlight as soon as possible. I guarantee you, once they own the market, guess what. Do you really think they're going to keep supporting the Linux and Mac (etc) versions? No, absolutely not. They can kill the alternate versions and people on the other platforms will be unable to use web 3.0 Gmail/YouTube/Facebook/Flick/yourfavoritesite. You'll be forced to use a MS platform if you want to use a mainstream 3.0 web service. This is the One Microsoft Way (their street address, coincedentially), embrace, extend and extinguish the competition.