If Mubarak falls, a lot goes with him, which is why Obama (under some good advisement evidently) the GOP and Israel are hitching their wagon to him. Its about balance, and maintaining it. You mention Iran as a balance to Israel ... perhaps, but at least you see the need for balance. I think the Dems are myopic in their stance, and missing the forest for the tree. And I think Iran isn't really interested in stability either. If Egypt falls, the balance will go with it, and that's a nightmare none of us want as its effecting even the stable moderate Islamic countries in the region.
It will effect the US, it will effect the 2012 election, the economy, the military, societies concerns over Islam, etc. Never mind the potential for lives lost. I think I'm agreeing with Friedman here that the choice will be the Republic or the World, and I would chose the Republic first.