I think that a tobacco ban is unnecessary at this point. Between the social stigma, the municipal bylaws, the health impacts and the cost, we've managed to make it pretty unappealing.
That said, I wouldn't consider a ban to be all that unreasonable, considering that smoking has killed upwards of 100 million people over the last century. I mean I'd definitely trade a smoking ban for an end to the drug war, if it came down to that.