Netflix's Watch Instantly first came to the Windows PC, and then to the Xbox. And, apparently Netflix loves being in bed with Microsoft so much they decided to scrap their existing online movie player in favor of one based on Silverlight. If you want to try the new Beta player, check this link out: http://www.netflix.com/silverlightoptin
How long till we see a player for Windows Mobile? I made an offhand prediction a while ago that we'd see Netflix on Windows Mobile phones within the year. A Silverlight implementation may make it that much more of a reality...