Chris Fahey discusses the merits of bespoke UI design, referencing the successful design of John King's touch wall which was created for King by Perceptive Pixel. Bespoke design--the practice of designing something specifically for and individual--might be more prevalent in the digital world than most people realize.
The examples provided out in the quotes of software designers and developers point out the most common case where this is happening. Designers who design products by focusing on what they want/need for themselves is common enough. What's being exposed here is probably not profoundly eye opening. What it demonstrates should be obvious to UX people who spend most of their time researching people (users) so they can empathize with them and guess what they desire. If you are your user, there's a good chance you'll be able to design the right thing for you. If you're a good designer, that is.
Designing for yourself means having the luxury to skip the middle man. It means you'll have a better chance of getting the right design. I think Chris' examples point out exactly why user research is valuable--because when you're designing for others it is not easy to get the right design unless you understand who you are designing for.
http://www.graphpaper.com/2008/10-26_designing-for-one-user-bespoke-user-interfaces