Naughty Nurse made a quick reference to this, but I think we really need to define "public" more finitely. I wouldn't ban smoking anywhere but for some there are boundaries. Is it at bars/restaurants/streets/national parks?
Bars and restaurants which are privately owned should make up their own mind if they want to be smoke-free or not. The patrons and the workers would be informed as to whether they want to dine or work at that establishment and market forces would decided if that working model was functional or not.
Streets are open air places and as such, it would be dubious to be that effected by second hand smoke on a regular basis.
National Parks, unless it would cause a fire hazard and that littering* is not allowed, I don't see the problem.
I am not a smoker. I can't stand smok. I do vote with my feet. If I'm at a bar and it's too smoky, I will tell the bartender the reason I'm leaving. Same way goes with a restaurant.
The effects of second-hand smoke are still unsubstantiated, but until corroborating evidence says it's safe, I'm still staying clear. That's just my preference.
*[soapbox]To all the smokers out there, the world is not an ashtray, when you're done with your cigarrette it is YOUR responsibility to find a waste recepticle for it. The ground should not be littered with butts.[/soapbox]