After reading "The Anarchist in the Library," it puts these cyber-attacks in a new perspective.
Now, Lobo Santo puts this into an interesting context.
Sit-ins, direct action, etc. all require an active, aggressive - sometimes non-violent - group action to hinder an ongoing issue. E.g., if you'll forgive the loft allusion, Rosa Parks sat in the bus actively, knowingly trying to make a point against racial segregation. In the process, she also impeded other segregationist whites from continuing with the status quo.
Anonymess, as it were, are making themselves heard, and for a reason. However, most of their actions are passive and collaterally affect legitimate "business." No customer will be presented (in the instance of PayPal) with a page saying that "PayPal is evil, here is why, this was done by Anonymous." Customers would be unable to access their funds for maybe a couple days. The sit-in theory is now bunk.
Back to the Parks allegory: these actions would be more along the lines of Parks sitting at the bus stop protesting segregation without actively stopping the segregationist seating policies.