First off, a lot of it is lazy press reporting DDoS attacks as a website being hacked. That was exactly what happened earlier this week, and instead of even using the term DDoS, many news outlets just said something along the lines of “Sony hacked again!”
To be fair, Sony has had their fair share of actual security breaches, the two largest being when PSN was compromised a couple of years ago and the Sony Pictures data breach recently. This is in part due to Sony making certain groups angry, ranging from actual hackers mad about anti-piracy steps to North Korea freaking out about an unflattering movie. Sony also seems to have made some poor security decisions as well. They had a folder named “Passwords” which contained exactly that: plain text passwords, for example.