It's not clear what exactly occurred. One one hand, you have someone claiming they took down GoDaddy using a DDoS (Distributed Denial of Service). On another, GoDaddy is doing a mea culpa. DDoS's and page defacement are not unusual. Even attacks against the DNS system, which could have had even more an impact than taking down a hosting company, are not unheard of. (Just rarer.) The only other groups of attacks I can think of at the moment involve espionage (black-hat hacking or corporate) or sabotage (eg. Stuxnet).
It's possible this is a case of Anonymous taking advantage of a vulnerability with the intent to cause harm. But if GoDaddy is willing to take the blame for a foul-up, I'm inclined to believe them as there's probably more shame in being the architect of your own catastrophe (an own-goal) than getting "owned". This equation flips for security entities (eg. NSA or -- hilariously -- HB Gary).
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