The advantage is that, while the reputation system is imperfect, it is one of the few ways of reducing risk and facilitating trade when dealing with digital cash. Escrows are imperfect too but if you combine the two you can achieve a great alternative to the traditional exchanges. It helps to decentralize the exchange process as well. If one or two big exchanges go down, the price discovery mechanism suffers - especially if there are no alternatives.
This also avoids the (possible) event where exchanges will be brought under the "know your customer" rules and you may have to provide identification documents and such. The auction format avoids the need to handle other people's money and this reduces the risks of future regulation.
this makes alot of sense.