Sure, they're probably lured in by this:
But 22 months, the top USD withdraw time, is ridiculous. 22 months from now, the $170 you sold your bitcoin for wouldn't buy five bitcoins on bitstamp. I just want to know; is it simply misinformation that has the Gox's volume so high?
Or maybe some people with big accounts have picked up the phone and asked mtgox to set something up for them. Then your assumption that nobody can get money out doesn't hold. These big fish are likely making bank on arbitrage, but smaller users have to buy btc to get out.