How often does a fast food drive through place make a mistake with your order?

I find it depends on which store you go to... one Wendy's is great, another Wendy's store has twice gotten my order correct, and once of those times it was CLEARLY BURNED and uneatable. I've stopped going to that Wendy's, all local Taco Bell and Sonic stores (at least in my local area... where I used to live they were alright for fast food, but around here they suck)....