The price of coming into the limelight, of becoming celebrities is always having some of your personal space and privacy constantly intruded. For television and movie celebrities this means being followed incessantly as they move about their daily business, and finding anything between pictures of them picking your breakfast cereal in the supermarket to lengthy discussions about why they wiped their baby's spittle with their left hand instead of the right on the internet.
For internet celebrities this means having you account's hacked, and not only you, but your family too (as is evidenced by the fact that Even William's wife's account was hacked too). You see, internet celebrities quite often, aren't beautiful people (sorry!), no one wants to see a picture of Bill Gates at a nude beach, but boy oh boy, if some wouldn't kill for his email password.
The principle remains the same though, it is a unwarranted intrusion into the personal lives of people, and any other justifications just do not count. What had the hacker to gain from information about he meal preferences of Twitter employees, or in fact anything other than information about their business' than the joy in embarrassing some of the key people who run this brilliant free service?
While the act of hacking into personal details is surely wrong, but exposing personal information that can only cause harm to people is despicable. What use is learning about Twitters plans for the future, if in the act you might deprive them of one in the first place?