http://blip.tv/oreilly-velocity-conference/velocity-09-maris...
Just watch from 1:00 to 2:00 -> One Minute will answer the question.
Here she tells the story, how the first Google Design came to live. It is quite interesting. It seems, that minimalism wasn't a rational choice and that it came to stay only, because the data proofed it to be the right lucky choice.
I can understand, that the minimalistic homepage was a point of pride. I would be proud, to minify the homepage of the company I work for.