Later that afternoon, my boss came in and said, "Ry, you don't know what other people are going through in their lives." The lead of the other team (who was in the meeting) had been to rehab for his crack addiction.
Similarly, I avoid using terms like "retarded". It all feels like shallow political correctness until you realize that there are real people out there with real things going on in their lives.
I tend to groan a bit inside where I hear someone make a remark about "smoking crack" because it's often used to describe behavior that is quite unlike that of a genuine crack smoker.
Anecdotally, of course...
You've probably heard of high-functioning alcoholics, it's entirely possible to a high-functioning crackhead as well - at least for a while.
I expect the point of exposure for most people comes not through continued use, but the point when something interrupts their supply. That's where they end up crushingly depressed, violently angry and indebted in ways that will surely screw-up the rest of their previously well-functioning life.
Only because it might compel some contrarian to build a space elevator. And I really want a space elevator.