This entire Asia Times piece by Bruce Klingner is a must-read, but this is the paragraph that leapt off the page for me:
The US is contemplating cuts below the already-reduced, 25,000-troop level announced for 2008, including a rumored total withdrawal of US ground forces by 2012. Defense Secretary Donald Rumsfeld and General Burwell Bell, commander of US Forces in Korea, have warned that the recent closure of the Maehyangri training range to US pilots could cause Washington to redeploy some of its military air units off-peninsula. Previous US announcements of troop reductions or redeployments triggered concern by Seoul over the impact on North Korean actions and investor drawdown in the South Korean economy.
I can’t recall having heard that rumor before, although I’m among those who believe that the U.S. ground component has outlived its usefulness. The rest of the piece is a very good summary of how South Korea has “balanced” itself into regional irrelevance.