Few support WMV these days and even MS has moved most of the focus on Silverlight. I was once the one of the biggest proponents of WM however, I really don't think they have kept up with the times and do not put nearly as much as they used to into this product.
About 2% of what we deliver is WM for adult now though we are one of the few CDN's who still support it. H.264 has clearly been the market leader followed closely by FLV.
However, Silverlight is seeing a turn around as many IPTV sites are moving to Silverlight. Nefflix uses Windows Media Silverlight. See:
http://blog.netflix.com/2008/11/enco...streaming.html