I think this is a very good image to explain how many companies add content to their websites. Layer upon layer, without the possibility to go up or down the information tree. Static pages with stale information and repitition, the user can't dig deeper into or understand the relationsship with other parts of the site.
A poster has clear constraints and it is within these the designer works. A website doesn't have these constraints, and I believe that more companies should focus on letter the consumer consume content they way they want to.