I've arbitrarily retagged six posts tagged "verb" to "verbs" since there were nine posts tagged with "verbs". Tag explosion is happening and taming is required????
Tag explosion is not happening, not yet anyway. You can blame me for the verbs/verb tags. There was an ongoing retagging from
verb; see this for background: Should we prefer singular or plural in tags? (Please participate in that question by voting or adding answers!)
As to why I didn't retag all of them at once while at it: well, obviously it's boring as hell, and humans are not made for this kind of work (and I don't have access to automated retag tools). So I started doing it in small batches. (Yes, I know the number of uses was not that big :-)
And even though the OP of this question (Shinto Sherlock) reverted the retagging that I started, we should do it again, unless plural comes out as the winner in the afore-linked-to question.
Sounds like a case for tag synonyms. Of course, with only 9 users above the required 1000 reputation, it might not be easy to get things done -- maybe the threshold should be lowered during beta?
In any case, I think the best option is to post here on Meta before a mass retagging. If enough people approve, it can be retagged and get a synonym. I'm sure moderators pass through here now and then to do the dirty work if there aren't enough regular users to do it.