Using user activity tracking data in application design

Gmail’s designers also saw that most people never use text-formatting options, such as bold and italic, when writing email, so they hid all those buttons under a single icon in the new window. In both cases, they used data to hone their designs to mesh with how people engage with the product.

That’s a new version of the “no one ever uses ‘advanced search’” line.

Using user activity tracking data in application design