There are a pile of tags associated with 3 or fewer questions. ("3" is not a magic number. It just seemed a reasonable number to consider "small".) Many of these look as though they should never have been created, because they are extremely "niche" issues... or "once-offs".
Why is this the case? Was the privilege for creating tags set too low at some point in the past, or something like that?
Tags is what it is since it's a folksonomy in the first place. That means that they should be built from the users and not by authorities, which in our case means moderators or SE-employees. They are a bewildered forest of signs without any control (if they are folksonomy tags only).
But our tags are in a loose way governed by privileged users and moderators. We merge tags, re-tag questions and delete tags that shouldn't be there.
But to say that all tags with three or less questions are inappropriate or that they shouldn't be there is generalizing too much. Every new tag had one question to begin with, and we don't know that this particular tag is something new or something odd. Does it really matter as long as the tag is valid how many questions is tagged with it?
I've made a few new tags based on interest, they are valid, but not very popular. Does this make them invalid? Out of scope? Tag count is a poor measurement of quality.
There are some natural laws "physics" (more precisely, dynamics) with crowdsourced sites, and one of these is the inevitable buildup of a long tail of cruft. If you look at anything from the vote distribution to the distribution of high scores on the site you'll see that same pareto trend.
Tags are subject to that same dynamic. There are a few tags which are very popular and a tremendous tail of tags which are barely used.
Unused tags are deleted automatically, so I used to try to retag questions which utilized esoteric tags....but it really is like cleaning out the Aegean stables.
Raising the privilege threshold for tags may help, but based on experience I think:
Stackexchange has plenty to work on, but I think a higher priority than cleaning up the tag creation process is for them to do a better job with the question interface because a lot of community effort is wasted on moderating, flagging and deleting lousy questions.
