Interesting BP piece posted to Deadspin earlier about pitch counts:
It's basic stuff, but there's some interesting bits about the nature of arm injuries in there:
Recovery days, a pitcher who doesnt get hurt, any of these guys youre talking about, have a pattern where they pitch, and then they have sufficient rest and recovery before the next time they pitch. A guy who blows out his arm, elbow or shoulder, doesnt blow it out from one day. What it is;he went through a season, or more seasons, where he pitched a little or pitched on a given day, and then he had recovery days and he pitched again, but he was never quite recovering each time, and his damage from game after game accumulated and became an injury.