I was thinking about this, and personally, I would use common sense were I adopting out a dog... and I'd obviously be VERY picky about my foster pups. ;D
Ok, first off - I would only adopt to some one who truly loves dogs, who is educated about dogs, and who is experienced/willing to learn. ANYONE who would fit into this criteria would definitely not be the kind of person who blows smoke all over their dogs and doesn't care. I would find it very admirable for the adopter to let me know that they do smoke, and be honest about it. But ultimately, I would not take non-smoking or smoking into consideration, I would solely base it on the dedication to the dog and the desire to give the dog a loving home.
Who is to say that a smoker's home is a "less than perfect" home??? My Mom smokes, and my dogs have never smelled anything like smoke, or have encountered smoke, in their lives.