SGExodus,
Tell us how you know for CERTAIN that the time-frame for someone to successfully withdraw their USD from MTGOX is "Let's say 3 months", as you espoused in your post?
Of course, I can't be certain. Any investment is about calculated risk and your own risk appetite.
For illustration, let us start with a modest $10k capital. This nett you 6% return from the simple arbitrage action, or $600.
Worst case scenario -- MTGOX shutdown and run. -- Lost all your $10K capital.
Scenario 1 - MTGOX took 1 year to process the withdrawal, but you eventually get the money back -- 6% per annual return, not great, but still beats putting the money in the bank for saving interest. You may also lost some opportunity cost along the way.
Scenario 2 - MTGOX took 3 months to process the withdrawal. Assuming the arbitrage opportunity still exists, and you repeat the process 4 times. 24% per annual return -- this beats most other investment instrument out there.
Scenario 3 - MTGOX took 1 months or less to process the withdrawal. Assuming the arbitrage opportunity still exists, and you repeat the process 12 times. 72% per annual return -- this is close to ponzi scheme type of return..
But it's your own money. You should do your own risk assessment.