Don't Make me Think
One of my favorite books on usability is Don't Make Me Think by Steven Krug. One of my favorite examples he presented in the book was the old BN.com “Quick Search” button. It left you wondering, even just briefly, if there was a more in depth search option that might take longer, but return better results.
Anyways, I saw a great real life example of poor “usability” at the mall near my apartment. You see, the way they designed the entrance to this mall from the main drag is a short little entrance that puts you on basically a loop around the mall. You are talking about 40-60 cars coming through this entrance on a green light, so clearly that entrance should have the right away onto that loop, and that's the way it is designed. The problem is that people for some reason assume there is a stop sign, even though the back of their car is almost on a 6 lane road, along with the 5 or 6 cars behind them.
The solution for christmas? They put up a sign. The opposite of a stop sign so to speak. The problem? The sign was red letters reading “Incoming traffic does not stop.” Now, I drive through this entrance once a day, and have for the past year. I almost came to a complete stop trying to read the sign, and then paused to think if I was the incoming traffic they were referring to. Needless to say, this sign caused chaos to people not from this area christmas shopping. People were stopping and even waving cars that normally have to wait for the stream of traffic off the main drag to go ahead.
This sign was up for 4 days. It has since been replaced by a sign reading “Don't Stop.”