There was almost a riot at SCL today. Everyone lined up neatly behind the sign showing their row numbers and then the gate staff rearranged the signs. Not once, but three times. People just started laughing at the agent trying to achieve perfection after shuffling to the new sign location. Everyone gave up and just formed one long line - which, strangely enough, worked.
I've seen this in action at BNE prior to boarding a 744 to LAX. Nicely formed two queues, business/priority and other (forgive me if the groups aren't exactly right), then the gate agent spins the sign around. Cue predictable chaos as some try to switch and some don't. Lovely.