They're basically running the back end of the game as if it is an MMO, which is fine by me given Diablo's history. Personally, while the whole rest of everyone is freaking out, I see this as the strongest move yet in the battle against a real problem in gaming (as opposed to piracy), which is gold farming. Blizzard is simply recognizing that people will find a way to pay money for items, and owning it. They've just taken the market away from those guys and put it in their hands and the hands of the players.
I really don't view any of this as being a DRM issue any more than having to be signed in to play WoW is a DRM issue. That's just the kind of game they're making. The online kind.
They are going to have to pump up their security even more now that real money is involved though. Not having an authenticator is inexcusable when someone could conceivably raid your Diablo bank for real money.