Apparently, some Palestinians in the Gaza Strip feel the urge to kill Jews greater than they fear retaliation:
Gaza militants launched two rockets into southern Israel Sunday, drawing a threat of "harsh and disproportionate" retaliation from Israel's prime minister and further straining a cease-fire that ended a devastating offensive in the territory two weeks ago.
To me, as long as Palestinians are willing to shoot rockets at civilian targets, Israel has not engaged in anything remotely "disproportionate."
I think it may be time to launch a sustained campaign to kill Hamas leaders wherever and whenever they can be found. Keep the drones in the air over Gaza as a constant reminder to Hamas leaders and to help with targeting.