I gotta say, the tag feature should be removed.
1. Not fulfilling intended purpose: The tagging feature was supposed to make posts easier to find and organize related topics. This has not been the case at all. Actually, I'm not sure that ANY of the thread tags could be used for this (other than ovis aries, and that's debatable).
2. Abuse: tags have become a way to anonymously and publicly attack other users. Negative rep is one thing, but the individual who receives the rep is the only person who can see the offensive language or attack. This board just doesn't have a place for anonymous attacks like "dv7eatsshit," "<femaleposter>isawhore," or any of the other needlessly derogatory tags present on the majority of threads.
3. Undermining the "open" purpose of the boards: these boards were created so that individuals could say what they want to say. The board culture has grown up around a group of mods (except for one; sorry, moonzzz) who claim every iota of information they distribute. These boards thrive on the open discussion, but are obviously injured by anonymous negative comments (anon. neg rep and the resulting negativity associated with bruised egos are a fine example here). Every individual who has professed to "need a break" from the boards or has chosen to publicly leave have cited this type of negativity.
4. Negativity outweighs any humorous benefits: some tags are hilarious. However, these tags may be actually undermining quality posting by proving a "slacker" posting vector. If a clever poster has an opportunity to make a funny comment, they will do so; either in the form of a post or a tag. Tagging merely provides another vector with which to deliver humor, but not one that is unique or special enough to outweigh the harm caused by truncating posting (i.e. the twitter effect) and anonymity (see above).
I'm all for free speech. If you want to say it; do it. If it's in the public domain though, you'd better own it.