Poor service I can deal with. Try getting food poisoning within a few hours after eating at what you thought was a decent restaurant. I had that happen twice in one year.
I actually had been poisoned, but probably not intentionally. A restaurant I would go to about twice per month was always indicated to me by others as having an outstanding offering for Thanksgiving. So, after a couple of years of hearing this we went, took some stuff home and refrigerated it immediately. By Saturday morning I was vomiting without anything in me and we hadn't dined out the Friday in between the holiday and that Saturday. I had the leftovers late that Thursday night and cramps all Friday before the vomiting began late on Friday.
Went to urgent care to get something to prevent the vomiting since the stomach was empty, but all in all dealt with six days of cold chills, sweats and cramps. Let's just say we hadn't gone back and it has been five years. We did email the company about it but they didn't even respond--they simply didn't care. And we were always one of their good customers but I guess that means nothing to businesses these days.
On the other hand we've eaten at Pappadeaux weekly (actually ~60 times/year) and have had about two instances of something not coming out perfect in almost a decade. I guess the general manager of the specific location and his crew (all really good people) just know what they are doing. The two instances weren't bad, just not great. We never complained and have repeatedly informed their corporate office of the great experiences. We've also been treated on the house several times as a result.
I guess it is just things like our Pappadeaux experiences that make such bad experiences so BOLD in our memories.