That CNN article is very general and vague; it doesn't cite any specific scientific reports - also, I'm speaking of marijuana only, not tobacco and crack.
"The nature of the marijuana-induced changes were also different, occurring primarily in the lung's large airways - not the small peripheral airways affected by tobacco smoke. Since it is small-airway inflammation that causes chronic bronchitis and emphysema, marijuana smokers may not develop these diseases"(Erowid)
"In an epidemiological survey, approximately 1200 subjects gave information on smoking and pulmonary function at two-year intervals. A large percentage of the subjects underwent pulmonary function testing. Although a small group who reported previous marijuana smoking had significant pulmonary abnormalities, current marijuana smokers had no significant reduction in any pulmonary functions."(Erowid)
"In 1986, however, the Food and Drug Administration had approved a drug in pill form which contains THC, a component found in marijuana, for treatment of that nausea. The marijuana lobby wasn't happy with that, or any other effective anti-nausea drugs. It became apparent that they liked marijuana for the high it gave them, not because of any perceived medical value. "
^^ The third article, which is hosted on AIM's website, is ridiculously biased, and even try to claim that medical marijuana is not beneficial, when I think most everyone with an open mind will agree that it is more helpful in preventing nausea and other medical problems than Marinol. Cannabis is a cocktail of various cannabinoids, with different benefits from synthetic THC.
EDIT: I'm not saying it's impossible, but there have been no documented cases of marijuana-only smokers contracted lung caner, and I have yet to see a study showing an actual link between marijuana and lung disease, other than "suggesting" that there might be one because of the tar content.