"Using the Popularity Contest package, these two projects
collect and post weekly anonymous reports about the software used
on each system on which they’re installed. The result is a
rare insight into the habits of FOSS users, including how often
software is upgraded, what applications are used the most, and the
differences between the expert-oriented Debian distribution and the
more user-friendly Ubuntu distribution.
"The main purpose of the project is to collect information for
installation, so that the most widely used applications can be put
on the first CD of an install set, or installed automatically. In
Ubuntu's case, the collected information is also used for software
ratings in Add/Remove Software."