1. Iran is now threatening to strike at any third country in the region that aided Israel in an airstrike on Iran. The aftermath is therefore likely to be further conflict in the region.
2. Oil prices will spike. I imagine you could easily see $150 a barrel or maybe even more. This development could throw the US and Europe back into deep recession.
3. Hizbullah would likely launch rockets, causing at least severe inconvenience to some 1/4 of the Israeli public, which might well have to move house again, and possibly much worse if Hizbullah is able, as they claim, to target toxic gas storage in Haifa or even reactor at Dimona with modified Chinese silkworms. It is not clear that the Israeli public would appreciate all that trouble; they didn’t, in former PM Ehud Olmert’s case (his 2006 Lebanon war was extremely unpopular and his party is no longer in power). A Hizbullah official said on Sunday that Hizbullah would be willing to go to war with Israel if Syria were attacked, so it seems likely the same thing would hold true with regard to Iran.
4. Israel would destroy Lebanon infrastructure in revenge for Hizbullah rocket attacks.
Juan Cole is Richard P. Mitchell Collegiate Professor of History at the University of Michigan. Please read the other six points at his blog.