These supercharger discussions always seems to loop around in circles, but the facts remains:
1) Yes, it is possible to encounter (or more usually on the internet, construct) some scenario where leaving your car connected at a Supercharger overnight seems like an acceptable, convenient, and even smart choice.
2) Regardless of reasons from pt 1, other people may think you are an asshole, and idle fees may apply. It most definitely is not proper charging etiquette.
3) Every scenario encountered/constructed in pt 1 may be inflicted by you on others if you leave your car plugged in overnight.
Personally I would charge to the required level when I arrive since it will be faster, and then move the car and go to sleep. I may even take a powernap while charging. If I was with my family I would drop them off at the hotel first, and then go back to charge.
Leaving a note with contact information is a perfect example of good charging etiquette, especially when at slower chargers. Wish more people would do that!
Anyone who is sleep deprived or otherwise unfit to drive and still gets behind the wheel is taking a huge risk, but seriously... the driver is at fault here and not the charger or charging situation.