Anonymous inherently uses fourth generation warfare strategies and tactics. One cannot bystanders from combatants, because functionally there is no difference. All one needs is to run the meme, claim the mask, and act as Anonymous. There is no top-down hierarchy issuing orders or calling the shots; there are cells which may or may not last, and which may or may not coordinate with each other. There are no bases to operate out of - anywhere one happens to be, one may operate (especially in the twenty-first century, with the advent of cheap personal computing and wireless access). Anonymous was the first to use media campaigns to propagate their memes and get people to actually act during the days of Project Chanology in late 2007. They are also adept at psychological warfare and media manipulation as part of Ops.
The IS is using many of the same strategies but most of their cells seem to be relatively inexperienced. That will change in 12 to 18 months.