When features go wrong
I spent last week in a hotel, where the bathroom lights were on a motion sensor. Walk in, lights on. Leave, and a while later they go off by themselves. On the surface, this seems sensible enough.
The Kano Model
Nobody has ever bought a mobile phone because it has a battery in it and yet nobody would buy one without. When categorizing new features, the Kano model is a way to organize them by how well they will satisfy the customers, against how much of it we need to implement.