Brokedown Palace, Part 1: Why User Guides Don't Work 

Software user guides use up an awful lot of space with screen shots. But I know what the screen looks like -- it's right in front of me. Any decent GUI design is self-documenting to some extent, at least. No matter how much we complain about them, GUIs have gotten pretty good. Children have them figured out in minutes. And then they start asking questions like, 'How do I make my stick man move around?' Computers are toasters or drawing pads to them. That's another reason user guides don't work: the average user doesn't need one anymore.

Knowles, Michael. Write Thinking (2002). Articles>Writing>Documentation>Screen Captures