If we wanted to go a step further, the regime is already on unstable footing. It wouldn't take a whole lot for us to disrupt the regimes forces, and let the Iranian people already in the streets do the rest. Having a few division sized formations set loose in the Iranian interior to help secure the major cities would go a long way. The greatest risk is the stranglehold the regime has on the mechanisms of civilized life. We saw in Iraq what happens when the trained bureaucrats pack up and go to ground. In this case I think there is enough opposition politicians to fill the gap, so that we can avoid a long term occupation. On that same note, thats why it is so vital at home to avoid dependence on government.