Considerable discussion of this, going back about a month, in this thread in MilesBuzz.

And I agree that the issue is not selling them, but stealing them. Selling miles violates the rules of most programs. You can lose the miles you sell, perhaps get your account closed and lose all your others, the person who buys them can find his/her ticket void when s/he tries to use it, but that's about it. The police aren't likely to get involved, and jail time won't be part of it. It was the stealing that got him into that kind of trouble.