Users creating tags without good reasons may be a problem (the example which I can imagine could be a problem - adding tag with name of PHP function by PHP developers) - in that case blacklisting would not help, you would have to create big blacklist with all function names etc. I would find good forcing user that creates a new tag to write at least (100, 150 or something) chars of description of that tag.
Do you have problems with tags you find improper, that are notoriously created by many users? In that case, why do you think a tag is improper, when there are many people who wants to use it?
A user can always create tag that is somehow improper. If so, he should be notified by moderator deleting or synonymizing that tag. However, if someone does that permanently, maybe he should be revoked the right to create new tags?
Anyway, by providing a few examples of tags that in your opinion should be blacklisted, and a reason why, would make it easier to discuss - I don't know if you had the mentioned by me cases in mind or something completly else?