I made some charts based on a big json file I compiled from all the currently existing tags that are in use.

The main thing to note here is that 80% of tags have less than 10 associated posts and that nearly half of the tags only use one post each.

Some other trend to notice is that there is a drastic drop in posts per tag when going from 10+ to 100+ posts. Also note the spike at the beginning and at the end of general tags, I believe the spike at the beginning is due to random typos, and made-up tags that haven't been aliased or documented and discussed yet. As for the spike at the end, general tags are used a lot of posts, I would vouch that if I checked the 500+ and 1000+ post categories, then the general tags would dominate and the artist and character categories would diminish rapidly.

(The non-overlapping proportional graphs make the most sense intuitively.)
The fun stuff