From the discussion above, the commonly justified reasons for prototyping are:

• To validate new science, technologies or processes: i.e. proof of concept.
• To validate that a product conforms to specific user, market and other requirements.
• Create a 'Feature Sieve' to separate good and useful features from bad and non-useful features up-front.
• To provide market demos.
• To provide quality / reliability testing platforms.
• To allow new feature / product analysis.
• To verify Usability.
• To test features before the design is sent into production.
• To point out mistakes or wrong-turns in: design, concepts, construction, testing.
• To pretest regulatory / safety design.
• To prove design value to users / market.
• To validate cost of manufacture (COM - components, testing, labor, overhead) since manufacturers can see, touch and test the prototype.
• To verify that appropriate materials and components are used.
• To verify manuals / written data.
• To verify product interfaces (human factors).

Whenever the prototype stakeholders are able to investigate a real thing by holding, feeling, smelling, viewing, hearing and trying out features and experiencing performance, a much greater depth of feedback can be garnered.

As friend Bill (Evans) puts it: "I cannot really get enthused about a project or product until I have seen a resemblance of the finished ideas / concept… I also don't believe the skills / ideas / and validity of the product and company until I see something. That to me is value"

Ahh…but, with the good always comes some bad…