Of course, one of my favorite papers by Cockburn about the vagaries of human performance, and especially when embedded on an agile team, is this one on the non-linear characteristics of people. I think you'll find this one a good read as well; and some provocative ideas to ponder.
Cockburn has given some serious thought to scaling the methodology. Agile is best suited for small teams that do not have mission-critical requirements. "Clear" is his "one small team" method. Crystal Orange, described in another book, is "Clear" scaled up a bit.
If you're interested in "Clear", here's a nice summary book report by Donna Davis that gives you a pretty good idea of what you are going to find in the book.
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