I'm not sure that I'd want to know everything about the people that I'm friends with on forums. Similarly I don't think I'd want them to know everything about me. One of the great things about the net is the anonymity. I'm a pretty normal person, but what if I wasn't? What if I was really ugly, or badly scarred, or really fat, or disabled? I know that people aren't supposed to judge on appearance, but that's not the way that real life works. On forums people judge me solely on what I write. There are no issues or race or gender. I'm not discriminated against because of my religion (unless I choose to post about it and make an issue out of it) or lack or religion.
The problem with Blizzard doing this is that with a quick few clicks you can pull up all the info that you need on people. You don't like a post someone made? Why bother with countering the argument when you can rather pull up a photo of them looking stupid.
Nah, I reckon this a rubbish idea.