I recently came across a web site that allows one to zoom into the content (it's a mapping site). Only the designers just assumed that everyone would have either a mouse with a scroll wheel, or a touch pad. Well, I have neither. And the developers of the site suggested "oh, just install this piece of software that allows you to bind some keyboard shortcuts to simulate a scroll wheel" instead of, you know, providing two damn buttons to zoom in and out! ("But ... but ... but ... adding those two buttons would destroy the aesthetic of the site!")