Can anyone see the disaster coming? Gaza is already one of the most densely populated areas in the world. Can one million people crowd into an area that is already occupied by another million people? Where will they stay? How will they get food, water, and medical care--especially since the water and electricty have been shut off? And what happens to the people who can't evacuate when the Israeli army moves in?
I understand that Israel wants revenge, but this isn't the way. So they invade. So they blow up a bunch o'buildings. So they destroy some Hamas bunkers and kill some Hamas fighters. What of it? Are they going to stay there indefinitely? Because Hamas will be back--they'll get some fresh weapons from Iran, extort their own citizenry for some more money, and slowly filter back into northern Gaza the moment the Israelis pull out. All those killed on both sides will have died essentially for nothing. The situation will be as it was before.
Do I have an alternative solution? Not really. A permanent blockade of Gaza and a heavy security perimeter seems to be the only way. But that has its own problems, aside from being hideously expensive. I don't think Israel can just bash the place flat and kill a couple hundred thousand people--I mean, they have the capability, but that would crush their image worldwide and make permanent, mortal enemies out of those Palestinians that remain.
I think it was Kurt Vonnegut who called the Middle East "God's monkey house."