In my opinion, its just the outcasts of the internet trying to feel accepted by banding together themselves to form the over-stretched anus of the internet.
Their DDoS attacks don't really have any affect at all beyond making them feel important and making them think that they can influence things on a global scale when in reality, they are at the bottom of the totem pole.
Sure, they took down the RIAA, MPAA, BPI and Scientology websites for an hour or so, and even managed to slow down Tumblr, but as far as I am aware, all these organisations still exist and are operating as normal. Their users may have been slightly annoyed for the duration, but will be back using their services again and will have probably forgotten the incident ever happened (or may not have even know it was a DDoS and thought it was just some down time).