Haaretz explains http://www.haaretz.com/hasen/spages/1121716.html In Israel, there is concern that AIPAC will interpret participation as an act against it. "You don't turn your back on someone who has acted in your favor for decades," said a senior Israeli official. "Certainly not in favor of an organization that has done nothing for Israel." The official added: "We have no reason to build up or bolster J Street."