A participant in the discussion about the recently dismissed McDonald's lawsuit asks, "Didn't tobacco companies deliberately increase the harmfulness of their products–specifically to boost their addictive qualities?"
As Jim notes in response, if anything boosting nicotine makes cigarettes less hazardous, allowing smokers to get the same drug dose with less inhalation of toxins and carcinogens. Another point to keep in mind is that, while tobacco companies do "manipulate" nicotine levels, in the sense that the way they make a cigarette determines its yield, there really is nothing sneaky or sinister about the process. Manufacturers apply nicotine to reconstituted tobacco sheet, for example, but the resulting nicotine content is lower than it would be if the cigarette were made entirely of tobacco leaf. In any case, the nicotine yield of each brand is advertised, so it's not as if consumers are being misled.
The charge that cigarette companies use manufacturing tricks to keep their customers hooked has a long history, by the way. Early in the 20th century, the secret ingredient was rumored to be opium.