Several people have recently linked to Diederik van Liere's talk "Learning from 10 yrs of Bugzilla data". If you're interested in that kind of thing, there's a whole sub-field in software engineering devoted to mining information about actual development practices from various sources. The best two places to start are:
  1. Kagdi, Collard, and Maletic: "A survey and taxonomy of approaches for mining software repositories in the context of software evolution". Journal of Software Maintenance, 19(2), 2007.
  2. Ahmed E. Hassan: "The Road Ahead for Mining Software Repositories". In Proc. Future of Software Maintenance, at ICSM 2008.
My thanks to Mike Godfrey for the pointers.