(1) Support by the public and lawmakers for the Patriot Act and other domestic policies legitimizing curtailment of civil and Constitutional rights, which was dwindling in Congress, will be dramatically rejuvenated.
(2 Similar support for the war in Iraq, and further potential pre-emptive strikes against other nations with a large Muslim population, will too, be dramatically rejuvenated.
The terrorists have given Bush and Blair exactly what they wanted, and needed, so badly. Read into that exactly you wish. Bushcorp and allies couldnt have wished for a better reversal of fortune. The toll of 50 dead and several hundred injured is a small price to pay for a potentially massive wave of public support for the Bush (and Blair/Berlusconi/etc axis) administration's worldview and corresponding policy set, which was given the green light by the 9-11 attacks. Coincidentally, of course.
A nasty thought, which I am sure has passed through many peoples' minds, is when the next terrorist attack mightl happen on the US mainland, for example, on an Amtrak train, or city buses, or shopping malls, etc, as in the style of the Madrid or London attacks? This will probably happen when the public regains a sense of reality after the support for the "war against terrorism" in the wake of the London bombings starts to wane. Paranoid? Maybe so, but it's probably a realistic guess. The architects of the attacks do have an agenda, with intense motivation, despite the impression that terrorism appears random, capricious and 'senseless' to the public. And the motive is almost always related to greed, fear, acquisition, power and control. The notable exception, of course, is the cult of the suicide bomber ... which is a symptom of a broken people in a broken nation, who have nothing left to lose, such as what is happening in Palestine and Iraq.
Every time there is an attack, and a corresponding imposition of extreme measures sold as "anti-terrorism", we know that the Bush crew, together with the terrorists, (whoever the hell they are working for), have won.