One of the many reasons why I think it will take a few more years before anybody should trust an exchange.
What's wrong with the IRC being the * only * way to trade BTC? It's stupid simple to authenticate your identity and the web of trust is a very strong point of the community of bitcoin users.
mtgox and everybody else (tradehill, bitmarket.eu, et al) have too many extra steps.
It's not the extra steps so much as they are insecure steps.