Since the vast majority of fifth round picks never amount to anything. Seems that the risk is non-existent to me.
Worst case scenario, he is a total bumb like Bwilliams says, and doesn't contribute. Certainly not far from what you expect from a fifth round pick anyway.
Best case scenario, he changes. It isn't like that doesn't happen. Jared Allen quit drinking. Eddie Kennison straightened up.
If your fifth round pick doesn't work out, it's a pretty minor deal.