Playing devil's advocate, the thing that these exchanges can, and often do, try to hang their hat on is anonymity. While through hard work (and lots of money) it can be "had" on the mainstream markets, financial anonymity is not something that you average joe really has access to on the major markets.

That being said, is that added benefit worth the (much MUCH bigger) risk of your money going up in smoke? Personally, I don't think so.

Overall, I agree... The reinvention of the wheel for the sake of it is laughable.