Only if it's truly decentralized. The Etherdelta situation demonstrated this perfectly. You can decentralize specific aspects like trading, but for as long as only one group is completely responsible for running operations (i.e. there's a point of failure), it can be exploited one way or another.
Is there an exchange that is truly decentralized? I'm looking for something like that actually. Almost every dexes that I know is running on a centralized web server and maintained by one person or group. Would be nice if there's an app where you can trade directly, just like torrent.