Scott Ambler and Damon Poole discuss how IBM scales Agile across large teams ( sometimes in excess of 500 people ), in an article
Agile development: It isn't just for small projects
While a brief article it does touch on one or two of the really key problems facing agile scaling; how to size and split teams into management units. As Ambler says "The architecture should be a system of subsystems." and therefore according to Ambler "the structure of the teams should be aligned with the architecture, and ideally the sub-team members should be co-located."
I have to admit that I always saw greater perceived value in creating teams that attack vertical slices through the architecture, ultimately these teams deliver end to end stories, and this worked extremely well on a major project I did for AOL. However at one of my current clients, this is just not feasible at this stage, the political makeup of the organisation and the inherent compartmentalization of existing teams, mean that its has been a major ( and ultimately impossible ) struggle to get a manager ( who once controlled his whole team ) to seed various functional teams with one or 2 of his assigned developers. We have therefore grown into a suite of teams split by architecture. Time will tell if this will actually work
