Performance improvements start to cost more and more to achieve smaller and smaller gains. So both absolute amounts of dollars, and their relative efficiency to purchase results, are limits on the policy thrust. The social world is growing increasingly complex, so the results of policy initiatives may be counter-intuitive. Other aspects of society that appear to have little or no relation to a problem, may nevertheless be effected by a policy or program. The intended target may even receive direct and important benefits, yet the subsidiary effects in other areas might leave a wider segment, or a more important situation far worse off.
Consequences are the future effects of present actions.
But because they are not immediately encountered, the possibility of adverse consequences can be discounted or just ignored. Consensus is the last limit, or more likely the lack thereof. Elections don't finish the campaign for social change, they only begin it. Public opinion must be continually mobilized to support each new initiative. There is no feasible way that programs can fully implement their ideological implications.