The problem is that since Dwolla dropped Bitcoin, there is no quick way to move fiat. If you have dollars on CampBX, you can indeed buy BTC and sell them for a profit on another exchange. You then have to collect those dollars, and then snail mail a money order to CampBX to repeat the process.

Even when (if) CampBX gets ACH transfers working, the dollar side of arbitrage will take about a week. With the current volatility that is an extreme risk if your goal is to accumulate Bitcoins. If you're ok with dollars you can lock in a profit.