After reading all the responses here, I am left wondering when the last time someone here who thingks the non-smoking rules at hotels are stupid/meant to be ignored, don't apply to them etc light up a cigarette on an airplane? If they haven't anytime recently why not? Clearly the law prohibiting smoking is an illegal one and anyone who chose to fight it in court would score a major victory for those who can't go 3.5 hours without smoking.
Personally I don't think that the rules don't apply to me, but there's quite a bit of ambiguity over what constitutes "in" the hotel. I would imagine that smoking on the plane's wing would be ok, assuming of course you weren't bound by the "no smoking on the Tarmac" rule. The wing is most definitely not inside the plane been though it's attached.
I do know several companies (my employer being one) who have nonsmoking campuses. You can't smoke in the parking lot; you can't smoke inside your car if you're on their property. At all of the ones I've seen, there's clear signage at the parking lot entrance, more signs here and there on the property, and all the ashtrays have been removed. While I'm sure they exist, I've never seen any hotel with a non-smoking campus/property/etc.
I suppose hotels are just trying to walk the fine line between pleasing non-smokers and pi**ing off the smokers by stating rooms and public areas are non-smoking but placing ashtrays at entry-ways (which implies smoking is at least tolerated at that area) and not stating a policy at all about the balcony.