Interesting on many levels.
1) When have you sent an e-mail so damning you felt the need to sue an e-mail host before anyone found out about it? ala "What the hell are they hiding."
2) If I sent you a letter to your house, I couldn't sue the Postal Service to come and destroy it.
3) If Google can just delete e-mails sent to you at a moments notice without consulting you, then it's probably a good time to start backing up your e-mail. What's to stop this case from repeating where a whistleblower sends an e-mail, gets immediately caught, and the data is deleted before read and the whistleblower is sent to jail?
4) Lastly, an elaboration of 3. You apparently don't "own" e-mail sent to you, if it's deemed accidental by a court. Which could be further expanded to you don't own anything in your inbox.
5) Side question, who owns the "sending" of an e-mail? Is it the sender, or the company he represents? If an employee sent an e-mail, would the courts consult the employee or the company? And what if the employee wants it sent?