this is an interesting idea that may necessitate a couple of new features. if there is an online shared POI DB, people may not want family and personal type POIs listed, and would probably want a local non-shared POI DB to be available.

depending on the level of effort, you could switch from one to the other, or maybe even have both shown at the same time.

i am sure things like common speed traps on interstates or traffic light cameras would be shareable types of POIs as well as sight-seeing vantage points and what not.