Unlike most I suppose I love the elbow room of public big woods and the challenge of not only of hunting the deer, but even the indirect competition with other hunters for bucks I'm after.
As I've already posted, I don't mess with cams I come across, whether left legally or not.
As for guys who perceive some claim to "their spot", that's exactly why WMA managers or other agencies don't want stands left on a tree overnight. Or rather, the last thing they want is a situation between two hunters getting out of hand. So has it ever occurred to you how A FEW guys might react if they had pics sent to their phone of some guy hunting "their spot"? And does it really matter if the guy hunting over their cell cam noticed it or not? What if he was so excited over the sign or came in before first light and never noticed it? That's irrelevant, but as for personal problems, it's hard to argue that cell cams on public won't eventually cause a few hopefully rare situations involving a hunter with personal problems.
As for the unsportsmanlike conduct you describe in your last comment as "the bigger problems", you don't think a cell cam could ever be the tool of choice?