look at the structure of dextromorphan

http://www.directopedia.org/onTEAM/w...methorphan.png

it has many of the structural aspects of a "phenanthrene type opiod", in fact, it's "levo" isomer is indeed an opiod narcotic. It has been known to give you a "wierd" high since it was put in OTC cough medicines after the FDA judged it an" acceptable antitussive (cough suppressant), without an abusable narcotic effect, having low activity at opiod receptors"
Since the 60's, when "hycodan" (hydrocodone) cough syrup became popular, it's abuse has skyrocketed. Prior to that codeine was the best of the phenanthrene opiod cough suppressants because of it's relatively low abuse potential, and they get around it by further lowering it's "appeal" by putting other ingredients in these syrups that make for a "nasty" high if you take large amounts in an attempt to get a high from it.
Used as directed, DXM is pretty harmless, and you can read about descriptions of the DXM "high" in places like EROWID on the net. My take on it is that it will continue to be sold, perhaps OTC, because it is usually a "one time trial" for most people, since it is not a "nice high" and there are far "better" drugs of abuse on the illegal drug market.