A very interesting aspect of this history is that Anonymous started out as essentially online pranksters with no political agenda. Eventually they would become more political and participate in true activist causes, always appearing in real-life protests wearing the Guy Fawkes mask from the film V for Vendetta.
The film also goes into how some of the members of Anonymous were identified and arrested for the cyber crimes (most often for "Denial of Service" attacks on websites) and were in danger of receiving prison sentences of up to 15 years, which is longer than what pedophile would spend in prison.
I have to admit that I found some of Anonymous' actions described in the film to be quite humourous. I think that despite doing actions that are technically illegal, they didn't seem interested in doing any permanent damage. However, the film also describes some a rival hacktivist group called LulzSec, which was somewhat more damaging and random with its hacks, which included breaking into the Sony PlayStation Network and stealing user info.
Before concluding, I should also note that the film included interviews with many members of Anonymous, both those whose identities were revealed by authorities and those who are still able to hide who they really are. It's definitely surreal watching talking heads featuring at least three people wearing Guy Fawkes masks.
Overall, while I wouldn't necessarily say that I agree with their actions, the film was definitely a very interesting look at this, still growing, movement.