There will be glitches when the major provisions of the Affordable Care Act are implemented starting Oct. 1. Huge glitches. Many glitches. Bet on it. That is a prediction not only from those resolutely opposed to the ACA. Even those quite excited about President Barack Obama's federal health law have the same expectation: The rollout of the biggest new social program in nearly 50 years is not going to be pretty. "When you're dealing with tens of millions of new clients, mistakes are inevitable," said Henry Aaron, a health economist at the Brookings Institution. "You're going to have thousands of mistakes."