Liberal ideas are almost always fraught with these unintended consequences. Take 30% of the population off of the Federal tax roles through the EITC, and the Federal budget grows exponentially. Become dependent on foreign oil by passing which prevent drilling, and the cost of energy climbs. Raise taxes on investments to increase revenues, and investing activity declines. Increase welfare payments, fewer people look for jobs. Cut the size of the military, and find the military stretched to its limits when it's engaged in combat.

Liberal ideas are always rather simple and intuitive. They make sense even to those who have little expertise in economics, public policy, and so on. That's exactly the problem. If you're not an expert in economics, for instance, then you may as well assume that there's more going on that you're aware of, and if something makes intuitive sense, then perhaps you need to look a little deeper.