I'm fairly new to the server (been playing for just a couple weeks), but my understanding is that chat spamming and auto-login spam has been at a high lately.
Now, I'm not terribly familiar with minecraft server plugins, but after the server crashin several times (or being manually shut down?) due to excessive login/logout and chat spam by some depraved individual(s), I thought it would be a good idea to at least offer a suggestion. The administration may have already examined this plugin (I can't find any mention of it on the forums or the thread search engine), but It may be worth presenting the idea anyway.
The plugin is designed specifically for spambot management. If a player enters a set number of messages in a set amount of time (e.g., 5 messages within 5 seconds, or 2 messages every second), the plugin takes care of the abusing player before it becomes a real problem for the mods and everyone else in the server. More interestingly, in my opinion, is that it seems to be able to ban players that join simultaneously en masse. (this part could have some drawbacks, due to possible innocent players joining during the spam, but i think it may be easier to manage that problem than it would be to manage 20+ players auto-logging every 4 seconds)
http://dev.bukkit.org/server-mods/antibot/It is a brand new plugin (March 4, 2012), but if the plugin is somehow old news to you, then I apologize. But i feel it is definitely worth suggesting, on the chance that it could be of some value. Also, I thought this might be a good way to kick start my activity on the forums :>
Anyway, I hope it at least peaks some interest. See you guys on the server~