I have wanted to, but have never done anything disgusting to anyone’s food. I just couldn’t bring myself to do that, and I’ve had some epically mean/cheap customers.
I will say, however, that I also live by the rule “you don’t ***** with people who handle your food.” I’ve been in their shoes. If I don’t like the food and/or the service, I still pay my check and tip. I don’t run to Yelp to bash the restaurant. I just never return.