It's hardly revenge if it wasn't preconceived. A decent lesson in due diligence however the title suggests that the Sysadmin intended for this to happen.
I don't know of any examples backing that stance up, but it is a perfect fear, uncertainty, and doubt, example that most upper management would never be called out on
"How I saved a company 100K a year after I was fired"
The employee could have debriefed his employer. Taken the moral high ground, and had an amazing story to tell at his next job interview + a lot of karma.
Or
"The importance of communication: How I implemented a quickfix without properly communicating the long term plan to anyone"