If you're already implementing messages like that another fun thing to do when the person goes way past the threshold is start making the site slow/buggy. Add i

If you're already implementing messages like that another fun thing to do when the person goes way past the threshold is start making the site slow/buggy. Add in random sleeps, redirect to a random valid or error page, etc. Basically make the site increasingly buggy. The added benefit is that is breaks any automated scripts people might be scamming with. That's what I did when we marked an account as obvious spam. Usually that was when an account was created and the same or next day sent 1000+ messages to random other users. Basically the person using the account would think the messages got sent but really they usually hit either a keyword/bayes moderation or a similarity throttle and the messages were put into a moderation queue rather than delivered immediately. Once the moderator picks "obvious spam", for that account the site gets buggier and buggier for 30 days until the account gets completely shut down and the person can't log in with it anymore. I did that for 30 days because I didn't want to warn them their account had been flagged and just have them create a new one. Basically it's a spammer tarpit.