1) anybody can go and submit ideas for software they'd like to use
2) other people upvote ideas if they like it
3) a developer takes ownership of any idea they find interesting and drives its development with an open source model
4) other developers join the projects they'd like to participate in, and contribute to them like any other open source project
However, the projects that get posted there have jumped a bunch of hoops to get there. A person posting there has got an idea, fleshed it out, committed to pay money to have it built, written a project description, expects a typically closed source implementation in exchange for money, and is comfortable with negotiating technical and project management issues with developers. It's not a workflow a non-technical, non-managerial average joe would be comfortable with.
What I'm looking for is a site where anybody can write ideas with no financial or other commitments. Developer(s) pick them up, work on them (only) with an open source model for anybody to use. Whenever there's a release, the system can notify the idea originator as a courtesy.