Design for real users
Chad highlights an excellent design perspective, "design for real people". Real people are rushed (at least in the parts I am familiar with), tired, distracted, etc. It is not those in the perfect lab setting that are important, but those actually living life trying to find the information for a report that was due COB yesterday, while trying to arrange for a new print cartridge from the help desk that never seems to (not my life, but one I have observed).
Maybe when we are doing user testing we arrange for phone calls and messages to be hand delivered. When I was doing usability testing on a somewhat regular basis, I always did the testing at the user's desk to see their computer setup and other things that may be interfering with usage. I have noticed that pale colors do not work well in workspaces with direct sunlight, which visual designers have used darker color palettes and reduced "I can not find it" complaints.