So my dad told me this story once,
He was working on a large, industrial construction project and they were nearing the end of it, so a QA engineer was scheduled to do a walk-through, and before that happened a higher-up purposefully damaged finished work, dented a pipe with wrench, unscrewed a bolt, etc... That way when the QA engineer did his checks, he'd find these obvious, easily fixable defects and mark them, whereas if he had found no problems, he would end up digging deeper, since he'll feel like he has to find something, and then he might potentially uncover some major, catastrophic problem that'd be impossible to fix and still hit the customer's deadline.
Theoretically everyone's happier at the end of it... QA because they did their job and found stuff wrong, the client cause the project was finished on time, and all that for an afternoon of extra work.
I worked for a company with an extensive QA process and on occasion I found myself being less then thorough before handing the code off. I knew there were bugs, but just left them in there, because they had bug quotas they had to meet, and we had a tight deadline, etc... At least that's what you tell yourself to justify the behavior.
Sometimes I wonder just how much of this kind of greasing-the-wheels goes on in other industries...