These limitations would be really helpful to you if you ever go to the Server Hall section of the Chat Room.

1) Users can only submit messages every 10-30 seconds (Reduces spam)
2) You can not post anything that is more than 4 lines long (Reduces Annoying Advertisements)
3) Set up filters that detect when messages are really advertisements
4) Removes messages that are considered advertisements if more than one is posted every 15 minutes (#3 must be added for this to work)

And more ideas to come. If you have any of your own, feel free to send me a message, and I'll see if I can add it to the list. Have fun playing Minecraft!