User Observation Testing is Mandatory
http://vaspersthegrate.blogspot.com/2004/09/user-observation-testing-is-mandatory.html

Streight, Steven
Blogger.com
2004

Abstract:

Without user observation testing, the usability of your web site is virtually unknown. Surveys are worth little, since those surveyed tend to tell you what they think you want to hear. Staff opinions are nice, but biased and they are not typical users. Heuristic (general guidelines-based) evaluation is helpful, but remains theoretical until tested on actual, representative users as they attempt to find information or perform tasks at your site.