Being confused why there no US based exchange at the moment, I did a little bit of history.

I read that tradehill was a US exchange that closed because of "regulations" and other issues ?!
I think coinbase would be much more legally liable than an active exchange since they are selling their own coins and not just facilitating exchanges...
Will another US based exchange thrive ? or are people too afraid of government regulations to invest in creating a USD<>BTC exchange ?