I did a short, and believe me *short*, stint at a company which provided on-line questionnaires. I was asked to provide a design for a questionnaire aimed at kids age 4 to 10. So I delved into the books, figured out how this group used websites, etc. Then I did a design.
Client wants to focus-group test. Fine. It comes back as completely inappropriate. He demands we re-do the entire thing. Mind you; this was after he got a research professional/designer when he was paying for a glorified DTP guy, after he got photo's from my own collection since he was too cheap to pay for stock and after numerous "one more little thing" extra's.
I guess he was right though; the focus group of 14 to 17 year olds hated the site...