[1] at this very moment I'm in my basement, hacking on some Lisp
OTOH , more uk government code is being released as open source. So in theory any developer could study the source and offer to fix bugs/add features and give a more accurate estimate. This might increase competition.
If you entered a bounty project with two hundred other entries (all of which have systems similar to yours), would you put hundreds of hours and all of your effort into the project in spite of the fact that there's only a 0.5% chance you'll get paid? Not if you want to stay in business.
The size of the project is barely even relevant, take a look at bounty programs that are up now for areas like design (99designs, etc) and how they are chastised for pumping out bad products from designers who are only putting a fraction of effort into the projects.
This type of system sounds great for those looking for cheap labor, but in practice it falls apart.