The one-page document from the Justice Department's cybercrime division shows, for instance, that Verizon Wireless keeps, for a year, information about which cell towers subscriber phones connect to. That data that can be used to figure out where the phone has been, down to the level of a neighborhood. AT&T has kept the same data continuously since July 2008.
.........A bill in Congress would force wired Internet service providers to keep records of the network addresses assigned to each subscriber for 18 months. That would help investigators link online activity to specific homes. But the bill doesn't apply to wireless links. A series of such bills have been proposed over the years, but haven't passed.
Read more: http://www.foxnews.com/scitech/2011/09/30/cellphone-carriers-keep-personal-data-up-to-7-years-report-says/#ixzz1ZW7HthYa