Wardish

Adjective: a technique, tool, or design idea that is clearly too ludicrously simple to be any good, but when you start using it has a power that belies its simplicity.

Examples include

• Discussing a design by moving index cards around
• A web site where anyone can edit any page
• Writing tests into web pages that will run and generate results back into the web page.

The name, of course, comes from the master of Wardish ideas: Ward Cunningham - who invented CRC cards, Wiki, and Fit.