Crack is whack, that much is for certain. But whether or not it's inherently addictive is a whole 'nother question. In a piece on addiction myths—vaguely related to the existence of Charlie Sheen, if you're into that sort of thing—Time Healthland's Maia Szalavitz explains that, statistically speaking, trying crack once is not a one-way ticket to a life of giving hand-jobs behind the 7-11.
Although crack cocaine is indeed one of the most addictive drugs, Sheen's statement about social use is true of most people who have tried the drug, if by "social" you mean use that does not qualify you for a diagnosis of substance dependence. Far from being universally addictive, crack is actually unattractive to the majority of people who've tried it: only about 15%-20% of initial users become hooked.
Indeed, according to data from the National Survey on Drug Use and Health, about 75.6% of those who tried crack between 2004 and 2006 were not using it at all two years later. Another 15% were still hitting the pipe occasionally, but not at levels that would qualify them as addicts. About 9.2% were addicted.
Now, that said, there's still plenty of good reasons to discourage crack use across the board. Not the least of which being the fact that a given individual has no way of knowing which category they'll fall into—Ho-hum or Hooked—until they've actually tried it. And for the people who end up hooked, that's already a bit a late.