Anders Ramsay has a great post on why he doesn’t use prototyping tools. His biggest problem with prototyping tools are:

• They’re based on the old, when design should focus on the new.
• They’re technology specific
• They create an illusion of a valid design

I don’t necessarily agree with his second and third points, or feel they’re not as important, but definitely agree with his first point.

At the same time, I think it’s important to keep in mind that most of these prototyping tools aren’t target at people like Anders and me — people who are quite comfortable coding HTML. These tools are typically intended for visual designers (e.g. Fireworks) or product managers (e.g. Visio, Axure). Not to say they don’t have value to others, but I do think they’re beneficial to the audience they’re targeted at.

Either way, if you use one of these tools, I’d recommend starting off on paper first so you’re not “bound” by what the software can(not) do.

Here’s a great example of real world prototyping from the inventor of the Strida2 folding bike.

Particularly interesting is how he discusses the prototyping process using sketching, mini models, and full scale prototypes at 1:10-3:15 and how he discusses the critical role of sketching while refining the designs at 6:30-7:15 in the video.

A few key points from Mark’s perspective:

• He doesn’t worry about which ideas are good and which are bad. Instead, he uses sketching to explore every possible idea.
• Once he has dozens of sketches, he evaluates the sketches based the original goals of the product.
• Sketches only go so far. The only way to really explore which ideas will work is to build models or prototypes.
• Sketching plays a critical part in updating the design as well. He uses sketches to work through his ideas.