Thanks guys. I have given a tremendous amount of thought to the subject of addiction and it's nice to hear that my deductions are appreciated.
To Asher, I think it's important to realize that although there is a large overlap between drug use and addiction, it is not necessarily hand in hand. There are plenty of people who use alcohol regularly and are not alcoholics. By definition, addictive behavior exists when it causes problems in ones life. The exploratory behavior of a psychonaut even with less novel states of consciousness would not be classified as addiction.
It really all boils down to the why. The answer often includes the defect if there is one present. I try to make a habit of always asking myself, "Why am I taking this?" before consuming any drug. If I'm taking some Tylenol it's pretty easy, but I can no longer provide a good answer for ethanol, so it's off the table. The more recreational and entheogenic substances are in the middle and often require some soul searching to justify.