Don't hire the firees
I used to work in the support centre for a major systems vendor. One key customer was having an abnormal number of problems and the team were asked to look into them.
Lo and Behold, one particular one of their employees was at the root of all these issues.
A lot of careful data collection went on and the findings shown to the boss at the customer's site. The problematic employee was asked to leave.
The next thing the support guys know is that this guy has just been hire by our company to work on major projects. He'd filled in a skills matrix claiming to be an expert on everything he'd broken. He'd listed the names of all the support guys who'd rescued his arse on numerous occasions as being references and the manager who'd hired him hadn't bother to check any of the references.
When they pointed out what a liability the guy was to his new manager the bloke wouldn't accept it and just said he needed heads and this guys was the best available.