“The phone number of every caller and recipient; the unique serial number of the phones involved; the time and duration of each phone call; and potentially the location of each of the participants when the call happened. All of this information is being collected on millions of calls every day – every conversation taking place within the US, or between the US and a foreign country. The government has long argued that this information isn’t private or personal. It is, they say, the equivalent of looking at the envelope of a letter. Because it’s not personal information, but rather ‘transactional’ or ‘business’ data, there’s no need to show probable cause to collect it.”
http://www.rawstory.com/rs/2013/06/05/what-telephone-metadata-can-tell-the-authorities-about-you/