If it happens again:
Go to one of these users profile, then to one of their posts.
Flag the post, use it needs ♦ moderator attention/other, and explain what you think is going on.
This is better than public shaming. You might be wrong, and this case it would be very unfair to expose the user in a public post.
The simplest solution would be for someone to retag one question with onedrive then we can merge the tags.
This will have the effect of retagging the rest of the questions tagged skydrive and automatically convert "skydrive" to "onedrive" when anyone uses it on a new question.
This has now been done.
I would tend to agree. Really the only way it has any utility is as a catch-all for any issue tracking apps that don't have enough questions to support the tag. (Tags on single questions get removed after some time.) But that's a really dubious reason.
I see you've done some clean up. I'll do some as well. If we can get it off of all questions it'll be auto-...
To do the rename you have to merge the tags which seems to have had the side effect of merging hangout and google-hangout into google-hangouts as well.
The cache takes a little while to catch up but if you spot any weirdness after a couple of days let us know.