The Law of Unintended Consequences is always in operation. Along those lines I recommend the piece Belatedly, Egypt Spots Flaws in Wiping Out Pigs by Michael Slackman in the Sept 20, 2009 New York Times. The Egyptians acted with the best of intentions, though with a flawed understanding of the problem, and got a worse problem as a consequence.
Is there a lesson in this for our current administration as it deals with financial problems, Iraq, Afghanistan, and health care reform? Certainly previous administrations have seen the same effect -- we helped the Afghan mujahideen defeat the Russians, and inherited Osama bin Laden and a core of experienced terrorists as a consequence. Congress (largely liberals, by the way) encouraged home ownership among those who really couldn't afford it and created subprime mortgages for that purpose, and as a consequence we inherited the current fiscal crisis, kicked off by growing defaults in subprime mortgages. We entered Iraq to remove a tyrant, and ended up stuck in the brier patch.
One might want to keep this in mind as Congress tinkers with major issues like carbon caps and health care reform. Whatever they do, and however pure their motives, the Law of Unintended Consequences WILL be in operation.