I'm not sure how "decentralized" exchanges would solve any issues. It seems create more issues.

One main reason an "exchange" exists in a one place is: speed.
If a buy-sell takes more than few seconds (or milliseconds), why bother with the concept of exchange at all?

On secondary points: Think about why an exchange exists: You trust your Bitcoins to the exchange. A p2p exchange is founded on mistrust. While it works for Bitcoin as an absolute currency, mistrust kills it for an exchange.

MtGox, given that is the defacto exchange, is bound to cause some problems. They just have to strengthen up.

Maybe someone can point out something I'm missing.

-SZ