It's a commonly held belief that professional photographers are asked to try out new camera models before production is finalized. Wrong. While pros may be among the first to see a new model, they have no more chance of altering camera features than you or I. During the design stage, pros (and trusted members of the photo press) may be asked for their opinions or ideas about features. But once the die is cast, we all take what the manufacturer gives us.
Looking back on the history of 35mm and medium-format film cameras, as well as digital SLRs, the manufacturers have a good record of success. Failures at retail have often been due more to a camera maker's financial problems than poor design.
But there have been some odd bumps and missed opportunities to advance camera design. And many have been caused by pros giving SLR makers misdirection during the design stage. Sometimes their opinions were (thankfully) ignored, but sometimes they were followed, resulting in problems that continue to this day. Here are some of my favorites: