Loadtoad. I actually think there's a significant difference. This isn't a search engine, it's a message engine. You sign up to get a quote. Other people sign up to give you a quote. I have no idea who the people suggesting quotes are. They may be professionals - travel agents. They can also be Joe Soap who happens to have booked himself a cheap deal once and THINKS he is now an expert. Flightfox seems to message their experts with your request and leaves them to get on with it. I'm also not clear how the reward is paid. If it's simply that you select a quote based on the price then you have no idea which flights they are suggesting - I'd want to know what routing/times were being suggested before I agreed to the finders fee being paid.
Like I said an interesting idea but many potential traps for the unwary and uninitiated.