And also, I shouldn't be keeping USD for any time either? How are you supposed to trade without keeping funds of either sorry there ready to buy/sell?
If you were in the US you can keep your funds in your bank account and buy through coinbase locking in your price immediately. Works for up to 10 or 50 coins depending on verification level.
As with all this crazy speculation stuff don't put anything in you can't afford to lose. Doubly so for funds held in these start-up exchanges. They're way more risky than simply holding bitcoin. I saw a statistic that at least 30% of bitcoin exchanges have closed down. Off the top of my head I can think of Bitfloor, Tradehill (twice), LibertyBit, Crypto X Change (took people's money), bitomat.pl (hacked, taken over by gox), bitcoinica (users funds lost, stolen, hacked, frozen, etc. lots of drama, just ask Goat).
Bitstamp was operating for a long time without any official requirements. You could just create an account with a fake name, etc. Then over night they required all these documents be sent in to them and if this was not done then no funds would be released. They do have the second or third most volume (which should be first or second most volume since USD can't be withdrawn from gox).
BTC-E is still run pretty much outside the traditional banking system. Don't know if they'll seek to get compliant but thus far you can create a throwaway account and trade there with no real ID. Because it's so hard to get $ into they prices tend to run a bit lower.
CampBX is registered in the US state of Georgia. Dwolla just dropped transferring to bitcoin exchanges which is temporarily hurting their volume (and perhaps price) but they're working on getting incoming ACH transfers going. They currenly will do outgoing ACH for $2.
Bitfinex is located in Hong Kong and they offer margin and some more advanced trading products.
If you don't want to deal with banking rules you could trade on some of the crypto to crypto exchanges like Bter, Cryptsy and maybe Vircurex.
Also there's localbitcoins and bitcoin-otc which are more resilient but not really for the active trader.