The recent high profile Distributed Denial of Service attacks claimed by the "Anonymous" group are
a) Only partially successful against targets such as as Mastercard, and Visa and PayPal etc.
b) Do not actually help WikilLeakS.org or Julian Assange.
Their latest stupid threats against Amazon and Twitter are indistinguishable from censorship of the internet, something which the "Anonymous" group pretends to be against.
A word of advice to those people gullible enough to download DDoS software, such as Xerxes or LOIC, even if it is used voluntarily: you should be aware that you have committed a crime with a potential punishment greater than that which Julian Assange is facing in Sweden.
e.g. the United Kingdom Computer Misuse Act 1990 was amended by the Police and Justice Act 2006 sections 35 to 38 specifically to cover Distributed Denial of Service attacks, by British or foreign national, either in the United Kingdom or anywhere else in the world.
The penalty for this crime (which is serious enough to be an Extraditable offence) is
"(c)on conviction on indictment, to imprisonment for a term not exceeding ten years or to a fine or to both."
i.e. an unlimited fine and / or up to ten years in prison i.e. more than the six years in prison which Julian Assange faces in Sweden for the alleged rape charges.
This also applies equally to the supposed "US patriot" hackers (who do not appear to have read or understood the First Amendment to The US Constitution, regarding freedom of the press) who have been trying, equally unsuccessfully, to counter-attack the "Anonymous" group or the various WikiLeakS.org servers.