Something that many people don't consider is that Blizz's online activity is a VERY different form of customer service. They have actually molded it into a marketing buzz. That is the most probable reason that they have thrown the standard form of customer service (i.e. always being nice and polite) out the window. Nobobdy wants to hear "Yes sir, we are trying our best to resolve your issue, blah blah blah".
Think about it. Look at all the discussion and buzz going around about these Twitter responses. Some love them, and some hate them. It creates discussions/arguments, and keeps the forums alive. I hate to admit it, but controversy really does sell. The more people talk about it, the more alive it is. If GC answered all questions in a calm & collective manner, they would mostly be quite boring. However, when he responds with some sarcasm, personality, etc..., all of a sudden there are discussions around it, perople can relate to it, people can hate on it, etc.. Overall, he's drumming up response. That is the benefit of public customer service. You now have a marketing tool. It has become it's own form of entertainment. Heck, some people spend just as much time on the forums as they do in game. So, it keeps their interest in the game even when they aren't playing.
Just something to consider.