And the code behind Silverlight can be any of the .Net languages(C#, VB, etc). Silverlight is more for programmers than artists like Flash. Thus, there is really not much of learning curve and it is much easier for actual programmers to get things done. I imagine that there is a ton more people out there that have downloaded Silverlight because NBC and M$ made a deal for Silverlight to be the app that delivered the live feeds and what not.