Just a short bullet list...
* International commerce through Suez canal
* Peace with Israel
* Oil and gas production exports
* Muslim Brotherhood rising (Islamo-Nazis)
* Fight against Al-Quaeda
* American made arms at the hand of its enemies
* American military presence along Red Sea
* Every western friendly Arab government falling
* Iranian cross Shiite-Sunni fraction domination
* Stability of the entire Middle East
* Africa - further destabilization
* World peace
Another thought, some have questioned what is motivating the rioters and whether the west should support them in their attempt to accomplish a revolution. To which, even if most of them are only motivated by social reasons, and are uninterested in religious fanaticism, the fall of the regime would leave a void - which the radicals are all too prepared to fill. This is precisely what happened in Iran, the radicals were a certain percentage of the civilian revolution. The Communists thought they would take the reigns, we all know how that ended.