Don't get me wrong, I love the idea, but...
I realize that governments wont be able to enforce a world wide ban to any great effect. However the can still make sure that bank transfers etc. cannot be made to buy/sell bitcoins. And if you can't buy/sell them for real currencies on a site like mtgox, whats the use of mtgox?
If mtgox is shut down, something else will be available.
Also, if bitcoins cannot be tied to a real currency, how would you know the value of it? How could anyone decide on what the value is without an exchange?
Outlawing bank transfers for bitcoin in the US will not stop the exchange of bitcoins for dollars. It won't even make it illegal to exchange Bitcoins for dollars. You could still sell Bitcoins for cash/check/moneyorder or gift cards in the mail, or goods or services.
So I could just set up an account in Switzerland and trade bitcoins legally? And then transfer them back to my home country? Somehow this sounds a bit like money laundering.
You will still be able to trade Bitcoins for dollars in the US. Barter is 100% legal.