A funny example of error prevention via pub signage.
The first sign "DO NOT EXIT" is at about eye level, followed by "UNLESS EVERYTHING IS ON FIRE" right below it and then at waist-level "JERK!"
This is the inside view of the main entrance to UCSD's Porter's Pub (I've always entered through there at least). There is a "back entrance" that they were using as the only entrance on Sungod where they had a guy standing and carding at the door instead of the usual carding at the bar.
Some people ran up to it expecting to exit through it and then after about 1 second ran the other way.