In Japan citizens are using google map technology to catalog areas of offending odors. The project called nioibu, is in Japaneese so i have to rely on the translations provided on Boing Boing. The principal is the core piece here - citizens are sharing experiences collectively and using an open API to collectively tag and mark experiences geo-spatially.
I have seen some very neat map APIs that catalog everything from personal experiences via the Yellow Arrow Project, to the national parks information currently on Google Maps. What we can learn from collective intelligence that appears on a need to know baiss is nearly limitless. The key breakthrough is that there is no need to absorb and store a globe of information, you get what you need about where you are instantly and seamlessly providing a rich and deep user experience. I have great hope for this kind of a project and look forward to seeing how this information melds with the greater geo-spacial tagging projects yet to come.