I smoke and I wouldn't allow anyone (and don't allow) anyone to throw any crap on the ground- butt or not, trash is trash.
Usually I give a friendly reminder if I see someone who smokes (a lot of people habitually throw butts on the ground, and have to consciously think about not doing it "hey, if you're going to smoke would you mind making sure sure your butts go in the trash?)). Second reminder is "less friendly" and come 3rd (if there is one) ... I'm not nice at all.
Spitting I don't really care about, so long as its outside off of common walk areas and such.