As much as the Israelis claim they can hit the Iranian sites, in my opinion, they don't have the capability to do so. Sure they have the training and technology capable of it, but they can't hit every single site. Plus the fact that the planes won't make it out alive. The Israelis aren't stupid, they won't hit Iran because they know it will be a death sentence for them. Iran would fire back, Hamas & Hezbollah will open up, Syria will jump and then all hell breaks lose. An Israeli strike on Iran is the worst possible tactical option they can do.
We're the only ones capable of mounting a successful strike on Iranian positions and we don't want to do that. Not to mention the fact they still a few years away from the bomb from everything I've read.
Edit: I even forgot to mention the fact that the Iranians would mine the Strait of Hormuz and really screw up the global economy. Hitting Iran is the worst possible option for everyone involved.