Microsoft? Maybe. But Netflix seems to have been working with both Microsoft and Google, and I think Apple, too, to make this work. So maybe they aren't just an idle player, and they may have been the ones trying to get the other major companies to do this for them (and others).
My guess is they (Netflix) are contractually bound by the studios to use DRM.
Agreed. Surely Netflix doesn't care ultimately, but studios are only going to sign contracts with them if they have things in place to guarantee it's all secure, i.e. DRM. There's surely no way that Netflix would fight for this, and then LOVEFiLM wouldn't use it as well?
Yes, but that's not an excuse for them to perverse the web so they don't have to use Silverlight anymore.