So, every now and then I see a post about the beauty of a decentralized exchange. Well here's the thing. You can't get USD on a Decentralized Exchange, adding new coins to trade will always be a headache, and since there won't be any censorship, scamming with new, random, 2 day old altcoins will be abundant, among other things
Decentralized Exchanges sound good in theory, but in practice it just isn't plausible.
I think that these are non-problems. A big market for decentralized exchanges are the altcoins. Also you forgot(?) electronic transfer for money (with all the problems today, I know).
Spam and scams are around here everyday too and still, it's a good forum and we got used to live with the goods and bads.
The actual problems may be the fees because every transaction means, as far as I understood, the coins to really move between wallets. In current exchanges you can make 1000 transactions or one big and the sum of the fees is the same. For decentralized... this may be a problem.
But still, I'd leave this idea get implemented for real. Then give it 2 years to get properly known and .. then we'll see how many are using it and if it was a good idea or bad.