I think this might be a bit of overkill for now, we don't have enough spotted posts to warrent methinks Though of course, can be implemented in the future should the need arise!
Gives me an idea though - could do a "Spotted Map" - like the events map, but you tag the places where you saw someone. If it turns out to be a member, they tag it as themselves and it keeps a little tally of who was where...