In one of her recent "mailbags", Astros beat writer Alyson Footer was asked right off the bat if we should be at all concerned about Roy O's pitching for Team USA in the World Baseball Classic. She answered that due to the pitch counts and the fact that Davey Johnson was an experienced manager, Cecil Cooper and the rest of us shouldn't sweat it.
In the 2006 Classic, major league pitchers actually were not used all that often. Over the course of Pool Play, the Second Round and in the Final Round, Bartolo Colon and Jae Weong-Seo led MLB pitchers with 14 innings pitched. The fact is that over a span of three weeks this is less than what a relief pitcher could expect to throw in a major league season. So I agree with Footer that this isn't the reason to be worried about future health issues with Oswalt.
What does strike me as being important, and is backed up in a study done by Nate Silver, is that these pitchers that do participate are away from their coaches that watch them every day of every summer and can pinpoint where their mistakes are with mechanics, delivery, etc. Silver notes that out of 26 pitchers that participated in the WBC in 2006, 19 had April ERAs above their PECOTA projection. While there have been several rule changes going into this year's classic, including an increased pitch count limit for each round, it's not the extra innings thrown that are the most bothersome by-product for major league pitchers.