Removing an item frame with a map doesn't remove the marker

If you place a map in an item frame, and then remove the item frame, the marker remains on the map. This enables you to use a single map to place many markers, which may or may not be intended, but also makes it impossible to remove markers. This could be a problem if you accidentally put one in the wrong place, or accidentally select a map instead of something else when putting something in an item frame.