Could really tall buildings provide a fire escape slide instead of the usual stairs? I wouldn't want to evacuate down 50 flights of concrete steps if I were in a hurry. I expect it would be a major selling point, too. The real-estate agent would bring you up, give you a tour of the place, then say "And here's the fire escape! Whee!" and you all slide down to the ground floor where your kids bug you until you buy the unit.
Mokalus of Borg
PS - It's probably impractical, in the end.
PPS - And a pain to clean and maintain.