Google launches collaborative My Maps editing
Say, for example you're planning a trip to Chicago with friends. You want to use Google Maps to plot the places you should visit when you're there. You can find a few destinations and add them to the map and then add your friends as collaborators and they can each add more points to the map.
You can also create a map that anyone can edit by selecting "allow anyone to edit this map." This feature could come in handy for conspiracy nuts plotting UFO sightings or recreational runners looking for good running paths.