Allow communal editing of photo tags
I have encountered many photos where the same person is tagged twice, or where multiple tags are not centered on any individual, or even where the wrong person has been accidentally tagged. The thought of allowing anyone to edit photo tags may be terrifying to some, but I can't picture it being any more prone to abuse than any edit to the shared tree. If tag changes were entered into the 'edit history' log along with an undo button, there would be an easy fix if problems arose. Double tags have become rampant since the site started auto-tagging all new photos. People don't understand how to edit the auto-tag, so they just make a new one.