Funny, powerful, but in the end true. If you were British and you used the metadata available to you to find Paul Revere you would be a hero.
So the takeaway is not really “is using metadata a violation of a person’s right to privacy” but instead “do the ends justify the means”. And the answer is: It depends on what side you are on.
Metadata is like a diary left out in a park. Sure it says private but it is left out in the open. Opening it is more a personal moral question rather than a legal one. Civilized society says you should respect ones privacy. But what if there was a young girl missing in the neighborhood? Access to the information in the diary may provide a life or death clue in the case. There is no way of knowing if the diary is even related to the missing girl unless you open it. Now the moral question’s weight shifts depending on how likely the diary is related to the missing girl. How close is the park to the site of her disappearance? Can her friends or family be interviewed to describe the missing girl’s diary? Is there a receipt for the diary sold to the girl’s family? We are told the first few hours of a missing person case are crucial to a happy resolution. Is there time for all the checks and balances to determine if we should violate the inherent and implied privacy of a diary or do we open it to see if it is hers or not right away? If it is not hers we can rule it out, closing and replacing it on the bench contents unread further and continue looking for the missing girl, no longer wasting valuable time or resources on this unrelated diary. If it is hers we can mass our resources to reading and deciphering the contents for clues.
So metadata is an diary left out in a public park. Eventually someone is going to look at it. Our best bet for privacy in a digital world is to have our diary next to a billion other diaries in the same park where only those with massive resources have the ability to sift through them all. If you are concerned about the NSA singling out your/our diary don’t leave it in the park and don’t write in it about your conversations with known terrorists.