At NetJets, the owners can smoke, but I've only had one in the last year who chose to. After the flight, a professional cleaning crew did a full cleaning and smoke removal, which is charged to the owner's account. Normally, as long as the mess doesn't do major damage to the interior, that's what happens. I've heard of owners getting asked to leave the program for completely trashing the plane to the extent it takes it out of service for more than a day or so, but I can't verify that.