Mental models are centerfold when dealing with interaction design. They form the basis of memories and experience that dictates the pre-decided subconscious paths people choose to take. However, equally important when designing is the consideration of short-term memory — the ability to overcome the shortcomings of natural attention spans of our society and keep users ready-at-hand with our designs — and ultimately lead them to their goals.
While it may be amusing to think of digital breadcrumbs, we must keep in mind that the best laid plans of mice often go awry. We must always design keeping track of sequences of our words and visuals, restraints and affordances of movement, and the cumulative cost of using our design. What cost? Time. Time is money, and the user will never pay if it’s too expensive.
We need to lay out our routes, routes that can be learned, routes that are efficient and guide the user and help them navigate the vast world of information we create on our spun web, and to make it so that the get their without forgetting what for, and make it so they get their without spending more time than they need to. The last thing we want is our designs frustrating — there is nothing worse than arbitrary loss — something that could've been avoided by simply not using it. We need the incentive of the user to carry forth their will into our route, and to make sure that they make it to the end.