Leadership in XP teams is only occasionally of the TeddyRoosevelt charging up SanJuanHill? variety. Normally, team members are swapping leadership minute-by-minute.
ReluctantLeadership is the title of a forthcoming book by KentBeck containing a PatternLanguage of emergent leadership techniques.
Did this book ever come forth?
What is your experience with different cultures in your teams? Many cultures discourage being the nail that sticks up which can make it difficult at times.
See also DeveloperTurnedManager