On the surface, many will point out that far more Palestinians have been killed in the past few days than Israeli's in the past few years because of cross-bombing. However, you have to point out the fact that Israel has been bombed on a day-to-day basis, and no matter how ineffective the bombs were at killing people, Palestinian group's goal is death.
Like in Lebanon in 2006, Israel strives for an improbable outcome. If things are to progress naturally, Israel will soon be sending ground troops into Gaza. After that, this will be not just a battle, but a (new) war. Does Israel want this? Perhaps, but let's hope not.
Possible reasons Israel may want war: Stop Palestinian groups from bombing Israel/protect its border. End the 100 years war against Palestine. With the growth of Iran and Iraq's nuclear weapons (and their hatred for Israel) perhaps Israel is trying to show they can protect themselves?
Whatever the reason, I hope it's a good one, and I hope it's worth it.