I don't really think that the people getting neutral feedbacks would care much about it as long as it is not affecting their account from the outside. You might find only a few in thousands who would take that feedback as a warning and stop doing what he got it for. On the other side, leaving a negative feedback to someone not clearly proven guilty for abusing the system sounds unfair too. So the better solution as said by a few already, would be to tag only the ones who are clear threats for the system, and have been constantly abusing it.