The American Civil Liberties Union has unearthed a Department of Justice document called Retention Periods of Major Cellular Service Providers (PDF), which documents the length of time that America's mobile operators retain your texts, IP sessions, call details, and copies of your bills.
Verizon, for example, keeps a list of everyone you've exchanged text messages with for the past year, according to the document. But T-Mobile stores the same data up to five years. It's 18 months for Sprint, and seven years for AT&T.
That makes Verizon appear to have the most privacy-friendly policy. Except that Verizon is alone in retaining the actual contents of text messages. It allegedly stores the messages for five days, while T-Mobile, AT&T, and Sprint don't store them at all.
The document was unearthed by the American Civil Liberties Union of North Carolina via a Freedom of Information Act claim. (After the group gave a copy to Wired.com, we also discovered it in two other places on the internet by searching its title.)