When you go to canada, you exchange USD for CD.
you buy ice and maple syrup and you have some money left over
so when you come back to the US, you exchange your CD for USD.
there ya go. this is how currency exchanges work, and this is how the bitcoin market works.
mtgox did implement a $500,000 monthly withdraw limit to preserve the market structure, but there are ways around that.
I've sold numerous lots and tried different methods of redemption, and I'm comfortable in my current setup if I need to bail out of the market quickly which I do not plan on having to use, but at least I have that option.
BTC just hit $250... happy trading
edit, markets in the EST are thriving this morning, $260.