A new idea.
I have started a new blog here, which I hope in the fullness of time not to end up managing. The idea is this. Can solutions to some big problems be brainstormed in a kind of "open" environment - as in "open source" - as in people finding solutions for the sake of finding the solution, rather than for their own glory or wealth?
Challenges will be posted on the blog, on which people are invited to comment. If people come up with helpful ideas in their comments, they will be added as contributors to the blog, and can write full posts explaining their ideas, which will hopefully draw more interaction ... and so on. To use it, you will need to register with Wordpress.
Incidentally, I chose WP because I've already done other things with it, and if the idea does take off, I expect to have to export it to its own website - something I would be more confident doing with WP than with Blogger.