And the bigger it gets and the more markets it expands into, the more it's going to have to comply with all sorts of financial services regulations and AML/CTF/KYC laws. This might piss people off, but they get more pissed off when they can't get their funds because Mt Gox accounts are frozen due to suspicious activity. If the exchanges don't comply with AML requirements, everyone's money which is held in their accounts is at risk of being frozen.
It's amazing that Mt Gox managed to operate for so long before this became an issue really. I expect that all the exchanges hoped they'd be able to fly under the radar for quite a bit longer. It takes considerable staff time and therefore costs money to verify accounts to comply with AML requirements and I'm sure the exchanges would rather not be bearing those costs during their start-up period.
The time has probably come where all of the exchanges need to have user agreements which clearly state that their customers may be required to verify their accounts and/or their identity at any time and that if they fail to do so their funds will not be released. The problem is that people rarely read complex user agreements such as those of PayPal and Technocash until access to their funds has been blocked. Even if the exchanges do have complex, multi-page user agreements I suspect that people are still going to bitch when the terms of those agreements are enforced.
I'm not sure about elsewhere in the world, but I know that here when a customer refuses to verify their account and/or identity to a business like PayPal or another financial service provider, the funds in their account must be transferred to one of the government unclaimed money funds after a certain period of time.