What are the limitations of corporations?

I think the limitations of government should be even greater than the limitations of government on liberties. The biggest argument against governments limiting liberties is the snowball effect, wherein we will turn into some Orwellian society with Big Brother always watching. I can see the worries that are brought up with this smoking ban put forth by corporations banning smokers from working there. This is a scary idea where the companies we work for can tell us what we can or cannot do. What if your employer said he wanted to save on health insurance so he said no one is allowed to eat candy, if they are caught eating candy they will be fired. That scenario is obviously extreme but it can show the injustices put forth by the corporations putting this ban in place. While everyone knows smoking is bad for them, company who believe this is a problem should put in place courses or councilors who can help them get better for their own benefit, not to help the bottom line of the company. This should not be a constitutional issue, but an issue of these massive global corporations to squeeze every last penny out of a worker and making sure they will not cost the company an extra dime.