News article on a senior designer at Google who's quitting because of not having enough latitude to design in the face of performance considerations.  From his own blog (bold mine):

When a company is filled with engineers, it turns to engineering to solve problems. Reduce each decision to a simple logic problem. Remove all subjectivity and just look at the data...that data eventually becomes a crutch for every decision, paralyzing the company and preventing it from making any daring design decisions...

Yes, it's true that a team at Google couldn't decide between two blues, so they're testing 41 shades between each blue to see which one performs better. I had a recent debate over whether a border should be 3, 4, or 5 pixels wide, and was asked to prove my case. I can't operate in an environment like that. I've grown tired of debating such minuscule design decisions...

Separately, this article talks about the kind of testing Google does to improve the usability of its products.

Noteworthy points:

• Users asked to be shown more search results per page, yet when more results were displayed, people searched less overall because of the performance overhead of the additional data.
• When the company trimmed the Google Maps page size by 30%, the company started getting about 30% more map requests.
• "Split A/B testing also led Google to refine exactly how much white space to pad around its logo and other elements on the search results page. And it changed from the industry practice of a pale blue background behind ads to a pale yellow background. People not only clicked on ads more, they also searched more in general..."

Kuler is a pretty cool application, although I'm not clear on why they decided on 5 colors per theme.  I decided to break my websites down into 5-color themes, and here's how they look.