In an article about iPad usability, Jakob Neilsen says this:

For more than a decade, when we ask users for their first impression of (desktop) websites, the most frequently-used word has been “busy.” In contrast, the first impression of many iPad apps is “beautiful.”

Busy, in case you haven’t noticed, is bad. It’s confusing. Unfocused. And leaves the user without a clear idea of where to concentrate his or her attention. E-commerce designers discovered long ago that 2-column Web page designs produced significantly more sales than 3-column designs. Eye-tracking studies, which suggest that viewers tend to ignore the third column anyway, reinforce this notion. Far from giving users more information, junking up the page with every last tidbit of information is not only wasteful, it’s almost guaranteed to drive users away with a bomb cloud of information overload. That’s not what you want.