I apologize if this isn't the correct forum for this.
It would be nice if mt. gox would go through the certification(s) necessary to be an online broker (like tdameritrade or etrade, etc.). I believe this would lend it a larger degree of legitimacy, and would probably ease the movement of money to/from the exchange. I'm sure it's expensive in money and time, but I think it would be worth it. They're basically behaving like an online bank without the burden of certification. Why not become a professional player?
Just to make sure this isn't overlooked -- Mt. Gox exchange is not based in the U.S. and has no operations in the U.S. other than a subsidiary Mutum Sigillum LLC of Delaware which is what the exhange has to make it possible to send funds to the exchange from Dwolla.
There are several U.S.-based exchanges: ExchB, Camp BX, and HelloBitcoin for instance.
As far as costs go though, the legal bills just to discuss what you are describing would probably alone more than offset the exchanges revenues on commissions to-date. i.e., Bitcoin will benefit more from 0.5% fees and a variety of exchanges to choose from than 5.0% fees and one exchange that is registered as a broker.