With the Private Messages give the ability to the "Leecher" user group to add message to your profile. So far i have had to delete 2 message within a day.
What i propose is set the requirement to post a Private Message to the same requirement to send a PM. If not we will see a tons of Private Messages in peoples userprofiles from the "Leecher" user group becuase they are unable to send the person a PM.