American made Surface-to-Air Stinger missiles have a built in safety feature. It is a sensor that detects friendly aircraft that ensures they do not target them. Hamas learned this the hard way in the their last war with Israel, Operation Cast Lead (Berman Post: Operation Cast Lead (Aftermath)). They found the weapons to be useless against the Apache helicopters Israel was using which the Stinger missiles recognized as friendly. In one reported instance, a Stinger missile was fired at an Apache. The missile veered of course, and then was attracted to the heat of a Hamas machine gun nest destroying it. Hamas stopped using the weapon and are now acquiring Russian missiles.
More at http://muqata.blogspot.com/2009/04/why-hamas-couldnt-shoot-stinger.html.
Hamas is now resorting to a more low tech attack, the Blood Libel just in time for Passover.
Video embedded below. (From http://jiw.blogspot.com/2009/04/hamas-blood-libel-jews-drink-muslim.html)