A Community Powered Map

I commute to work for almost an hour and a half and sometimes when I try to go around the metro, I have to use my psychic powers. Then during the day, it's always rush hour so finding the best route isn't that easy.

So why not make a community-powered map? When I was in Hong Kong last summer, I reached the destinations that I was planning to go to through their directory. But since we don't have complete and accurate data on the locations (that is official), why not build our own?

Community members can post road congestion, traffic patterns, locations, suggestion to routes and roads. The site could then create some uploadable file for GPS or other navigating device (I don't have one so I don't know how this works).

A WAP version should also available. It would probably work better if community members could send and recieve road traffic conditions via SMS (because, like most people, I don't have money to pay for GPRS).

For validating user-uploaded content, the community will have to rate the quality of a post. There should be a moderating group too (just like in any working organization).

Would this work? Will an overlay map for Google Earth suffice? Trapik.com doesn't work for me. This would help with further localization (read: not just limited to the metro).