The advantages of mock-ups (and prototypes) are numerous. For example:
Mock-ups incite criticism from users because they are low-cost (can be made of cardboard) and low-fidelity. If a user is presented with an early version of a system that has required substantial work, he/she is likely to be more reluctant (as well as able) to critise it.
When using mock-ups of cardboard or similar materials, the user and designer can collectively change the design using familiar tools such as pens, scissors etc. As such, mock-ups are a discussion medium and a discussion facilitator between designer and user.
Not only can the mock-up function as a discussion medium between designer and user but also between the members of the design team. Thus, mock-ups may help facilitate work across disciplinary borders, bringing together a disparate team.
