Anonymous has a lot of big protest events, where people go and wear masks, carry signs, and block traffic. Their protests are advertised as improving society by resisting things like police brutality or Scientology. And if all they did was assemble in the real world and perform nonviolent protest actions, I would not object to them. Americans have the right to protest.
(Some people say that Anonymous has done good things that really helped people in other countries like Egypt and Tunisia. That may be true--I know nothing about what happened there. My topic is what Anonymous does in the USA and UK only.)
Anonymous has a serious organizational defect--there are no rules, no formal membership, and no way to eject people who do harmful and illegal acts. So, as in "Lord of the Flies", the worst elements multiply and gain power unchecked.
Anonymous has become an organization famous for senseless and cruel acts on the Internet. Here is a list of some of their outrages:
Dumped names and personal information of police informants
Dumped Arizona police passwords and emails
Dumped email addresses and passwords of BART commuters
Dumped emails from H B Gary Federal
Dumped 150,000 email addresses and hashed passwords of US military personnel from Booz Allen Hamilton (the 90,000 number in the article is an understatement)
Dumped passwords and encouraged members to log into email, Twitter, and Facebook accounts and harm random innocent people
Anonymous does not stand for any cause. They just attack all authority figures and cause as much harm as they can to gain bragging rights. They do not plan protest actions to achieve a goal, and target people in any logical way. Instead, they just attack anything that seems in any way connected with any unpopular organization, and dump all the data they find, harming innocent customers, employees, victims of previous crimes, etc.
Stay out of Anonymous! If you want a career in Information Security, people need to trust you, and that will be very difficult if you have a felony conviction. Even if you do not personally participate in criminal actions, it is a very unwise career move to be connected to a criminal organization.
If you want to join a protest movement, join one that forbids crime and harming innocent people, and that ejects people who do those things. Anonymous is just a lawless destructive mob and does not deserve the support of good and honest people.