Gamasutra managed to corner Blizzard Entertainment's Greg Canessa for an interesting interview about the challenges involved with building the modern, why the company needs their own online platform, what sort of functionality they might add to it in the future, and more.
Why does Blizzard need this platform? Why not just use something like Steamworks?

GC: It might make sense [for other companies]. It really depends on the platform and the opportunity. If you're in the console space, you really don't have a lot of choice. You really have to use one of the game services. They do a really good job, right? If you're in the PC space, there are a number of different solutions for you. If you're looking out there and you want to deeply integrate with a game service, there's Steam and Steamworks. is very focused on Blizzard titles today -- but who knows, in the future? There are other services out there like Games for Windows Live. There are a few players.

In the iPhone space, that was really kind of what I was thinking about. There is more opportunity to innovate, I think... You have Game Center. This has come along recently, but you've got OpenFeint and [Ngmoco's] Plus+. Those guys are willing to work with individual game developers, even small developers, on some really unique integrated scenarios that I think are more akin to the integration that I was talking to.
StarCraft II worked great in multiplayer, so it's comforting knowing that Diablo III will be hitting the ground running for those of us who want to play cooperatively on day one.