Aw, and here I was thinking of ways to get around it. By taking snapshots of the activity list and the map list periodically one could have eventually figured out which points belong to which members. If the location error is random, one would even be able to average that out over time and get a very close location. If it's not random, then one could figure out the offset with a few tests.
Not that I would have done that (too much work, and for what?) but it's fun to think about security holes...