There is a recent post on MO that includes two new tags: Beer and Bet! The problems of these two tags aside, I don't think it is a good practice to add new tags unless it is absolutely necessary. Is it possible to add a feature in which a number of MOers (for example, three users) should agree with the introduction of a new tag before its use?
Such a system would be technically impossible since we can't delay posting a question until tags have been approved. However, this is not a serious problem:
- Only users with at least 300 points can create new tags.
- Users are quick to delete inappropriate tags from posts.
- Unused tags get purged in 24 hours; single use tags get deleted after 6 months.
- Moderators and some users regularly check newly created tags for problematic cases.
There is no need for additional measures.