Question: Is there some way to tell who has created which tags, and when? If a method doesn't exist I would petition SO to add this, as I would very much enjoy seeing tags I created being used by other people. 

SO must track creator meta-data on tags since a badge is awarded for creating a tag used by 50+ questions (taxidermist).

Answer: 
There is nothing in your user page that will help with this, but following the chain below you might be able to figure out if you asked the first question with a specific tag. However, I'm not sure how retagging and/or deleted questions are treated in relation to the taxonomist badge.

`Tag -> sort by newest -> last page -> question on the bottom`, should be the earliest question asked with that tag, but still not guaranteed that that question or that user created the tag.
This is now covered by the **Taxonomist** badge.

To see a list of all those with the badge and what tag they created (so long as it is still in use), check out the [Taxonomist](https://webmasters.stackexchange.com/badges/11/taxonomist "putting tags in your skin so you can eat while you freak") badge page.

To see what you alone created, check out the bottom portion of your user profile.