Why Contemplate Bombing Iran?

On Foreign Policy's blog there's discussion about the possible bombing of Iran.

How can we even contemplate such a thing, when we're trying to add more troops to the conflict in Iraq?

And hasn't the Iraq quagmire convinced us that pre-emptive strikes are not good policy? We found no weapons of mass destruction in Iraq; if we bombed Iran, would we then say "oops, their nuclear program was exclusively to generate civilian nuclear power"?

Why don't we resolve Iraq and keep Afghanistan stable before contemplating further attempts at destabilizing the Middle East.