It was this person who was already doing milder illegal drugs. He goes to his dealer and dealer proposes something different this time. He decided to try heroin. Had pretty high confidence he wouldn't get addicted. Anyway he describes his first try. Then as weeks went on he periodically posted updated. He kept justifying going back to trying it. Gets addicted. Long story loses his job, girlfriend, goes into rehab for a long time. Pretty harrowing story.
EDIT:
Thanks to japhyr56 who found the link:
http://www.reddit.com/user/SpontaneousH/submitted/
Or this one?
http://www.reddit.com/r/IAmA/comments/jcxow/iama_functioning...
Anyway the idea was that many go in thinking they can handle but it turns out they can get addicted the first time and it can ruin their life pretty quickly.
Cocaine can't have actively put you off that much if you did it again a few times. Reminds me of the joke "Quitting smoking is easy. I've done it lots of times."
My best (and personal) example is that I would smoke a cigarettes with friends back in college whenever we were out and drinking. It provided a good additional buzz and it was somewhat social. I'd even buy my own pack so I could have one if my other smoking buddies weren't around (also when I was out drinking). I averaged 2-4 cigarettes per week and I'd even go weeks without smoking as well. It was sporadic and I didn't enjoy cigarettes any other time. When I saw people smoking during the daytime I would actually be kind of disgusted at the thought of smoking. So I guess my point is... was I addicted? I don't think I was. Was there ever a line that I would say that I "quit smoking"? Eventually I did stop my "casual" routine. Even now, I think I would still smoke a cigarette if I was put back into similar situations.
I think it's completely reasonable to have tried a drug many times and not be considered addicted. On the contrary, many of those same college friends I smoked with I would consider to be addicted. It wasn't a limited activity. It was an anytime and anywhere activity.
I guess for most people it is more like "there's so many movies about this stuff and famous people take it, it MUST be good, I need to try".