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: 
I have a list of which users created which tags, but Jeff has said he doesn't think any good can come from disclosing this information. I may be persuaded to help you if it's regarding a specific tag or user, but I won't help you if the tag has less than 50 occurrences. 

In the general case nothing from SO will help you in finding such information, and you'll have to compile it on your own.
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.