From Wiki:
To exchange cryptocoins right now, you have to sign up for an account on a centralized platform such as Cryptsy/BTC-E/Bter/etc, transfer coins to them and then pay them for transactions. This brings in a large concern: its possible that the exchange could just bail with everyone's deposits. This recently happened when the Sheep Marketplace did just that with 96,000 bitcoins. The developers of Nxt are developing a peer-peer exchange into the software to allow for decentralized trading which will eliminate this trust point. It will also eliminate trading fees! Obviously this is all still completely secure and anonymous as are current bitcoin transactions.
Or you can look at the video, 0:56:
http://www.youtube.com/watch?v=zALTChPsXhQThank you, but, I still don't understand how they are going to achieve that

Something Ripple style with the gateways problem?