The widespread introduction of the personal computer, beginning about 1970, helped spawn the field of inquiry called cognitive engineering, which concerns itself with such things as interface design and user friendliness. Since then, this field has taught us many important things, including two major lessons. First, the road to user-hostile systems is paved with designers' user-centered intentions. Even smart, clever, well-intentioned people can build fragile, hostile devices that force the human to adapt and build local kludges and workarounds. Worse still, even if you are aware of this trap, you will still fall into it. Second, technology developers must strive to build truly human-centered systems. Machines should adapt to people, not the other way around. Machines should empower people. The process of designing machines should leverage what we know about human cognitive, perceptual, and collaborative skills.