There are a few ways to combat this:
- Require a tag to be used by 50 users and not 50 questions.
- Rate limit the use of re-tagging by the same user.
- Require a week 'cool-down' period after the tag is created and used by 50 questions until the badge is awarded. It should give plenty of time for other users to spot gaming and revert.
- Get rid of the taxinomist badge. It has invited more than its fair share of controversy.
Regarding the user in question, I asked him via Stack Overflow about the tagging. He responded:
Yup...went on a tagging spree... However, I didn't do it with the intent of inducing erroneous tagging, as ideed, gps technology is a subset of telematics. Telematics, or telemetry, is a technology that allows remote measurement and reporting of information, thus including a wider variety of fields than just gps: en.wikipedia.org/wiki/Telemetry. I stand by my action, as further questions targeting the integrated use of telecommunications and informatics may very well choose the tag as a valid one. – luvieere 6 hours ago
Take that response how you will.