Do you really think that if Bitcoin exchanges were closed down, the price per coin would go up? I'm just asking a hypothetical question; I don't actually think that the exchanges will be closed down. Imagine if tomorrow, Mt. Gox announced that they were being shut down. People would be scrambling to sell their coins and get their dollars back in the bank.
Most people involved with Gox would probably scramble, but then afterward, anyone looking for BTC (even those that previously scrambled) will be happy to pay an exorbitant premium for them, from Shades McBitcoin down on the corner. People WANT monetary freedom EVEN MORE than they want pot, and they want pot quite a bit...
When I stayed in CA, near San Jose, there was a certain hydroponics store I became friendly with the employees of. (sue me for ending that sentence with a preposition.)
Anyhoo, the OWNER of the store (who was himself a huge pot head), voted NO on CA's prop 19 (outright legalization of marijuana), BECAUSE he knew if prices did not remain HIGH (LOL PUN), his store would likely go out of business.
Prohibition of a high demand product = huge price markup.