Seriously, you people who are apologetic about this must believe every computer on the planet is completely compromised from the moment it's turned on. No other service seems to have this degree of problem, and a lot of them have a hell of a lot more at stake than D3 does (pre-RMAH, at any rate).
Again, if keyloggers were so prevalent the entire internet banking system would have collapsed by now.
Besides the fact that you know really fuck all about the severity of this problem to compare them to other services properly, it has absolutely nothing to do with the online banking system. They aren't even comparable situations.
First off, to actually do something with a compromised bank account you have to send the money somewhere. Even ignoring the fact that step one already places you into a serious federal crime, you've engaged in a system that is designed to be one of the most traceable in the world. Moreover, when you can directly steal money from someone through this system using
much easier information to steal like they're fuckin' credit card number, it becomes a questionable thing to want to stick your very obvious hand directly into someone's bank account.
Yes, most of these online banking accounts have better password systems, but the vast majority aren't any more secure against keystroke recording than any other online account. The actual difference entirely comes down to the ecysostem. Very few people even want your online banking login information to get to your money because it's a terrible way to get to your money; everyone that wants to get into your Battle.net account absolutely wants your login information.