This is also evidenced by Amazon.com still looking really crowded and ugly. They test every last thing and if this is what they're using, it's because it works.
This same concept goes for those horrendously ugly, cookie-cutter, inline sales pages plastered with maroon Comic Sans headlines that have highlighter-yellow backgrounds. I've been there and done that, and the facts prevail. As a good/(as in one that creates aesthetically pleasing things) designer, you actually suck conversion wise.
I haven't done much research behind it, but I believe this has to do with why the flat UI is so pleasing. I can only imagine that it is easy for anyone to notice that it's beautiful regardless of technological/design experience/knowledge.
