Dwolla may or may not have something to do with it. It people are putting funds into MtGox via Dwolla and then rapidly trying to withdraw via wire transfer, that should definitely flag their system as potentially fraudulent/ML activity and trying to limit their exposure to potential reversals is not just reasonable but essential to the best interests of all customers. A lot of payment processors won't let you withdraw money via a method you haven't previously used to fund your account and the exchanges may very well end up having to put such restrictions in place eventually just to stay in business.
What you said might be true, if I popped out of nothing, DWOLLA's a million bucks and then tried to wire them back next day, that would have definitely be something to take a note of.
But when your customer, who does transactions on a daily basis, for a year, requests a 100 bucks wire? Under circumstances that make it clear, why that happened (e.g.: outrageously long withdrawal times?). I think it's a pretty fishy thing when THAT gets delayed for a week.
Most companies keep their funds in this or another form of bank. The wire transfers should never be delayed if funds are available. This is why there's so much suspicion in this thread.
Another thing with DWOLLA transfers: as I said I've been verified with MtGox for a year. I sent them my ID a long time ago. What they did with it, I don't know, but now they canceled two of my DWOLLA transfers, citing their policy, and had me re-upload the documents AGAIN. And guess what - they didn't cancel it right away, instead they waited until the payout time. then they canceled it, then after I uploaded the documents, I'm back at the end of line.
All of it looks very fishy...