Microsoft can't necessarily build an ecosystem. Remember PlaysForSure for music? Yeah, those people got reamed when Microsoft dumped it. And not many besides Zune owners have heard of its incompatible successor, the Zune Marketplace.
2 and 3 are reasonable, especially 2. Microsoft has traditionally been pretty good at leveraging customer bases to enter others -- look at the illegal leveraging of desktops to get into the server market. Now they'll be going the other way. Microsoft can really do this right in the enterprise. Within the next couple months, before the Surface is out, they need to release a free update to SCCM that fully controls both Surface editions. If that update isn't already beta, some manager somewhere needs to be fired.
I remember all that. But then I also remember XBOX Live, the best video game online system on the planet, which has been hugely successful, and not just for gaming either(at which it excels), but for all kinds of content delivery.