Joe Sheehan has a tremendously important article (not subscriber-only, for once) -- with some data I hadn't seen before -- explaining (at least partly) one of baseball's greatest mysteries: why pitchers can't throw as many innings as they used to. Without direct pitch count data, Sheehan approaches the question from a variety of other angles, noting the steady long-term rise of walks + strikeouts/game, the dramatic recent spike in power production from players on the right end of the defensive spectrum (catchers and middle infielders), which raises the stress levels on pitchers who have to fear the longball all the way to the bottom of the lineup (the DH rule has also contributed to this). It's a must-read.