Honestly, it's a matter of laying out a few dollars for proper legal counsel, and adopting the proper compliance. It requires a modest outlay of money, but there is absolutely no reason why an exchange should fail to do this.
Based on previous discussions about this issue - including comments made by Mark himself when MtGox was looking into MSB registration last year - the FinCEN registration is relatively simple but the state level registration can be extremely expensive and difficult (and state level registration is required in the vast majority of states).
Although the specifies failure to register with FinCEN, the code itself also makes it an offence to operate without appropriate state licences whether or not the defendant knew a licence was required.
18 USC section 1960 (b) (1) (a)
While the funds in the Wells Fargo and Dwolla accounts can only be seized once, that doesn't mean MtGox can't be fined for violations other than the failure to register with FinCEN (on that violation alone they're potentially looking at a $5000 per day fine for the period during which they should have been registered because every day they fail to register after the first 180 days of operation counts as a new violation)
I don't think anyone who's ever worked in financial services would regard compliance costs as "moderate" or the compliance process simple. Large institutions invest millions in compliance and they still get fined massive amounts for getting it wrong.
