Here's the snopes.com story
http://www.snopes.com/inboxer/scams/jiffylube.asp
So true!
I go to a cheap franchise place for oil change and watch every step. They know I'm watching and I've never seen them skip a step. Then a while back I saw them print "Transmission fluid looks dirty- recommend change" on the work order *before* they looked at the car!
Another customer argued "how can my transmission fluid be dirty, I took my car elsewhere and got it changed right after you advised me on my last visit". They changed her record in their computer so that won't print on her invoice for a while.
I take my car to my real mechanic when I need real work like a transmission flush - I trust him.