Oh, those crazy kids and their fascination with certain members of Lamiaceae. For some reason, the media has gotten all worked up again over Salvia divinorium, a tender little sage that, when chewed or smoked, delivers a short-lived and sometimes unpleasant hallucination. It's cheap, legal, and widely discussed on the Internet, making it better-known to teenagers than their parents.
The DEA itself will tell you that under a million people a year use the plant, and their own information suggests that the effects are hallucinatory and short-lived but not much more. (I've read some accounts of hospitalization after S. divinorium use, but those may have been frightened kids who really did not enjoy the trip.)
On a federal level, the plant is legal but listed by the DEA as a "plant of concern." Some states have banned it, most haven't but stories continue to bubble up about the possibility of a nationwide ban, and this USA Today piece quotes a state legislator as saying that "There was no legitimate purpose for that herb, and the things it was being used for were potentially harmful."
So. There's the test. If a plant has no legitimate use–whatever that means–and if it could potentially be used to harm one's self or someone else, as any one of thousands of plants could, it should be outlawed.
So what's next?