I was sending someone directions to my office, and I noticed that the placemark that Google Maps puts on the map of the office address is more accurate. It used to be nearby on Route 9, but is now exactly on my building.
Back in November 2007, Google introduced a feature to allow editing of addresses and other information by anyone with a Google account. When viewing a placemark, you can now click "Edit" and move it to the right place. You can also see the history of the edits, which appears in this picture in reverse-chronological order.
You can see Google's original guess with the gray arrow in the lower picture. It looks like it was moved three times: to the right spot in November, a little off the right spot in January, and then back to the right spot in March.
Community editing is often abused, but I'm coming to expect this degree of interactivity from websites. When I see something amiss, I'm frustrated when there's not a "submit correction" or at least a "flag spam" link. In this case, I was the happy beneficiary of my peer's contributions.