I think you're forgetting that a corporation did not send these emails. People did. As others have pointed out, these emails include a great deal of very personal information that have nothing to do with Sony the corporation, or any other topic of public interest.

If Wikileaks had reviewed these emails and released only the ones that are of genuine interest to the public (or did not disclose sensitive personal information), as it did with the Manning leak, that would be one thing. But I can't agree that it's responsible to release the entire trove of emails simply because they were sent to and from corporate email accounts.