A large part of the justification for the county smoking ban in restaurants is that children accompaning their parents cannot freely choose to not eat in that restaurant. (Note that this doesn't really apply to the city ban in bars, unless one is concerned about minors with fake ID's being exposed to secondhand smoke.)
How long before someone decides that the worst threat to kids is parents who smoke? Some city in California will probably be the first to use secondhand smoke as an excuse to take kids away from their parents. The nanny state will soon become the legal guardian state.