I'm convinced now that if Microsoft wants Silverlight to really take off, it is going to require more than paying websites like MLB to use it. An individual developer working on a small scale business is unlikely to require someone to do an extra download of Silverlight to use their site. Users won't do it, and they'll often go to another website.
In the early years of the intertubes, I refused to do the extra download of Flash or Java. Flash was only used for advertising. Then it was decided that Flash was going to be used for things like menus and video players, so you couldn't avoid installing it. Either way, we have a world where 80% or more of web users have Flash installed and 0.001% have Silverlight installed, if that many.
So why not put Silverlight into Windows Update and boost that number to 90% having Silverlight installed? Why not ask Apple to put it into Mac OS X Update and have it distributed to all mac users? Apple and Adobe aren't exactly a love-fest anyway.
I think Silverlight and Flash should be made to compete on technical merit. All that is required to do that is get Silverlight out there to users so they won't have to do the extra install step.