The most interesting thing to me will be if pirates are going to be able to get around the online DRM. I doubt they will. It would be an interesting challenge and I suspect that the only way to do it would be emulate Blizzard.net. Also because of this online DRM requirement, Blizzard has painted a big bullseye sign. There will be people who will be trying to launch denial of service attacks of some kind on Blizzard.net so that legitimate customers will not be able to play to make a point about this kind of DRM. And I'm saying now, that if people are prevented from playing because of the online requirement, there will be hell to pay and there will be a ton of vitriol thrown against Blizzard.
I guess I don't know if Blizzard.net has been attacked in the past with any success.