Hope no-one minds me butting in on this, its basically true what Loosehead has said, but they,(the Palistinians), know what the reaction will be, and want it, don't forget, they still have 'The Destruction of Israel' on their mandate.
Because of their mindset, they will, every so often, provoke a reaction that they hope will unite the Arab world in a war against Israel, and also turn world opinion against them,.
They don't mind how many innocents die to achieve their aim.