I had to think about this thread when today I, oddly enough, stumbled over not 1 but 2 blog posts regarding water faucets and taps:
<a href="http://mattmorphett.blogspot.com/2009/01/sometimes-there-is-good-reason-to-break.html" rel="nofollow">http://mattmorphett.blogspot.com/2009/01/sometimes-there-is-...</a>
<a href="http://www.malcolmcoles.co.uk/blog/usability-taps-lessons-web-design/" rel="nofollow">http://www.malcolmcoles.co.uk/blog/usability-taps-lessons-we...</a> (via <a href="http://www.uselog.com/2009/05/checklists-and-water-taps-for-usability_28.html" rel="nofollow">http://www.uselog.com/2009/05/checklists-and-water-taps-for-...</a>)