Haddon said that when researchers combine their studies to produce a single paper, each scientist depends upon the honesty of work contributed by the other co-authors. That, he said, is the way science is supposed to work. I'm sorry, but if I were going to put my name on a document, especially as a co-author, I would make damn sure that everything in it was correct and provable. (walking away, shaking my head)
Trust, but verify.
I have removed my name from papers where I though the rest of the work was shoddy.
On the other hand, I always try to describe my results and methods in enough detail to allow independent verification.