NameIsRobertPaulson said:
I think he means that people would hack and steal accounts in WoW, sell off the gear.
A RMAH only encourages this practice.
One could think that's what he meant, but then he went on saying that people who are good at last-hitting will "steal" their teammates loot (like in WoW and most other MMO's), which just isn't the case in Diablo 3 as you don't have to last-hit enemies to get loot. Also, you can't steal teammates dropped loot/items when they die.
Someone hacking your account, however, is a whole other thing. If one would have an insecure password it's their own fault. There are also authenticators you can buy or download free to your smartphone (at least iPhone and Android).
And to use the RMAH you have to setup a cellphone to receive codes to enter when using the RMAH. You also get an SMS for suspicious login attempts, etc. etc.
But sure, there's always a possibility, but then again, there's a possibility that someone will break into your home and steal your stuff too. Probably even a higher chance.
But again, he was talking about last-hitting to get the loot, which just isn't the case in Diablo 3.