Shifting information goals
Peterme nicely illustrates shifting goals in the information seeking process -- complete with screen shots -- revealing the complexity of navigation design: 'My original "goal" was to learn about Ann Willoughby. On reading that page about Ann, my goal shifted.... Shifting and evolving goals are not only common -- they are the norm.'
Someone at work recently pointed out that the retail theory people, like the folks at Vanderbilt's eLab, tried pinning navigation to the measurement of flow. It's another example of a highly dynamic environment (psychology + HCI + lots of information) that makes simplistic approaches to navigation design look, well, simplistic.
I took the first step to addressing this with my navigation design research and method. It needs a lot of work, but I think it approaches something robust enough to acknowledge the complexity of navigation design yet accessible enough to use without interfering with the design work itself.