Very tough quesion to answer. I know someone who uses heroin once per day and has done so for the last 8 months. My best friend has used cocaine on the weekend for the last 3 years, then once his child was born, he just stopped. While their isn't no certain type of personality or 'addictive personaliy" as they say, there is definitely something that seperates these types of people who can use recreationally, from say, myself, or everyday addicts.
I am going to go out on a limb and say that one thing many addicts have in common, but not all, is we have poor emotional coping skills. Drugs help us bypass the thought process of examining our own problems.
On another note, anything can be addictive and harm ones life, right down to something as stupid as jacking off.

Of course their are some chemicals that are worse than others. Drugs that mimic, manipulate, or change chemicals in our body, are usually much more addictive that ones that are just a chemical added to our body, or a chemical that doesn't already exist.
One example would be the methamphetamine molecule and dopamine, another would be Morphine and endorphins.
There really isn't an answer to your question, but their are plenty of governments and scientists with statistics.
