To give you an idea, i have put in sensible bids for hundreds of projects. I have had one response from a dodgy Australian, who refused to give out any details of the project - in case we gave the game away.
I think the problem is, its a lot of people putting in stupid bids like £50 for a 1 week project. Thus completely taking the bottom of the market out for any serious small businesses/freelancers.
And im sure in many cases, where you can post a project for free, its other freelancers, trying to do some research into their competitors.