Recently I've been hearing from Adobe on a regular basis about adoptions of the Adobe Flash Platform by large media organizations, such as Clear Channel Radio and, for streaming media content to the Web both live and on demand. I've been hearing rather less from Microsoft about Silverlight adoptions.
I think that part of the reason is that Adobe leapfrogged Microsoft last winter in the area of media support, particularly H.264/Advanced Audio Coding (AAC) audio and full HD video playback. These and many other capabilities are included in Silverlight 3, which is currently in a beta that does not include a "go live" license, but will most likely be released in July.