I would have to say it depends on the situation. If one were to hire someone for the job of maintaining security and they still are engaged in illegal activities, it could become a liability. On the other hand most of the great security guru's out there played both sides of the field at one time or another. People grow up, move on, but you are the one responsible for judging their motives. Is it better to have someone who can look at all angles or a college graduate with no real world experience who can't see all the dimensions? If I weren't an administrator myself I would choose the one who thinks in code not just reads it.