Interestingly, O'Leary posted a picture from PitchSmart (a movement from USA Baseball preaching ways to keep pitchers healthy) which says that pitchers who compete more than 8 months per year are 5 times as likely to suffer an injury requiring surgery.
Oh, and to clarify what I meant in my above post (it may seem contradictory) the point about year-round pitching is more geared towards young guys and its impact when they reach the professional ranks. The mechanical issues apply regardless of age, pitching schedule and other outside factors. If your mechanics suck, you will eventually need surgery. That is a fact without many exceptions.