There's an interesting article in MIT Technology Review titled "The Decline of Wikipedia". The author takes a close look at how Wikipedia operates and notes that the volunteer workforce that built and maintains the English-lanaguage Wikipedia site is growing smaller. Why? The author notes that "The main source of those problems is not mysterious. The loose collective running the site today, estimated to be 90 percent male, operates a crushing bureaucracy with an often abrasive atmosphere that deters newcomers who might increase participation in Wikipedia and broaden its coverage." He cites a detailed study of Wikipedia by University of Minnesota, Berkeley & Washington grad students that details various problems with useful graphs and charts.