I worry about it, but my son's not a full-time pitcher, so these other folks know a lot more about it. We didn't worry about it when he was younger, and he had some growth-related overuse injuries until about age 14. His arm is now finally doing great, and I don't want to see any other overuse injuries.
I think part of my worry is that 2B only pitches occasionally (he is MIF/3B), so coaches don't have him throw pens, or work with mechanics, or anything like that. But when he does pitch, he can be very effective, so they leave him in there. He pitches mostly in relief, but started 3 games in 2009, and won all 3 - 2 were complete game shutouts. 2Bdad got me a pitch counter for last Valentine's day (he's a hopeless romantic!
) and I use it. He got close to 90 once, and 2Bdad was ready to go take him off the mound himself, but the coach took action.