1) A "ToS" (Terms of Service). Right now there are trolls, spammers, and flamers all over the forums, and AFAIK the only person to be banned was that university student who flooded the FFXI board. Any quality forum needs to have rules that are clearly displayed as well as consequences listed. This brings me to #2:
2) Moderators: there's like 5 admins covering about 50 boards made up of thousands of threads and millions of posts, and right now the only way to report abuse is manually. Users can report abusive posts to moderators through a form or the moderator can delete (negative karma) the post directly.
3) Purge: with no purge eventually the storage space will run out, plus if you think about it there is one "classic" thread for every hundred or so. In fact you can check by changing your filter to "Excellent Only" and threads per page to "100" and seeing how many on average appear. You could either purge by thread rating or just by time (ie. Sub-Default threads are purged after 24 hours).
You can discuss these suggestions and/or add your own.