Thanks for starting this. My current thoughts after moving ideas between different statuses:

From Sandbox to Under Consideration:
- At least one week old.
- The idea itself has more than 10 karma points (e.g. 15 thumbs up and 4 thumbs down) http://maemo.org/community/brainstor..._actual_ideas/
- Contains at least one solution to vote.
- It can be demoted back to Sandbox if solutions are mixed with the proposal description.

From Under Consideration to Under Development
- The Maemo team has incorporated one of the solutions proposed to a public roadmap or
- Proof of work from any development project exists, be the team from Nokia, the Maemo community, related upstream OSS projects or any other third party.
- It can be demoted back to Under Consideration if the work is clearly stalled or abandoned.

From Under Development to Implemented
- The solution is available to pure end users through a stable release distributed through Nokia supported channels including maemo.org.
- It should go back to a previous status in the case that the software released is not distributed anymore, is totally unmaintained, etc.