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This follow a similar theme to the link I shared when asking for permission to add people to this list, and further emphasises the importance of using measurement rather than gut feel, but discusses it in the context of current design trends and what happened to a real website.
In this case he is discussing horizontal layouts which are popular because they look elegant and are easy to adapt to small screens. The problem is that real world experiences show they can work worse (in terms of selling).
Also, in the case he discusses, an experienced team did not get the results they expected. They found the problem because they did A/B testing. It is important to look at actual data - traffic, heatmaps, conversions and conversion paths etc.
I also came across another interesting link about why bad software is profitable. It is a good statement of the problem, but does not provide any easy solution. It also reminds me of another great quote I came across recently: "Walking on water and developing software from specifications is easy, if both are frozen"