What's the greatest evil drug prohibition or drug addiction?

I believe the greater issue is prohibition. Whatever the intention of legislating what substances people can or cannot use, the primary affect is the denial of choice. Most of it is meant well, but it still amounts to the limitation of peoples rights. Most now illegal drugs were at one point legal and in common usage. For them, it wasn't their effects on people that was their downfall, it was that their usage was considered sinful or distasteful.