One thing I found interesting was this:
Now call me a luddite but for me gaming has always tended to be a form of escapism, it's about getting away into another world, not one which has some kind of social network that lets your mum msg you that dinner is ready from her phone. Furthermore, in case it has escaped blizzards attention, gaming has done pretty well with it's own networks over the years, whether that be ICQ, IRC, forums, xfire/steam etc. And those in themselves can be somewhat escapist, when I'm online I sometimes just want to be "HangTime", not the real me, I don't want to worry about saying something that'll make me look stupid at work the next day.
At the end of the day, if you want some kind of social contact with people online, you are not going to say to them "hey, look me up on Blizzard RealID xyz", you are going to say "here's my email/msn/facebook/whatever".