T-Mobile has yet to issue an official statement on the matter, but word on the street is that hackers have found their way into T-Mobile USA's inner workings and made off with a treasure trove of information, including subscriber data, which would make sense considering that parts of T-Mobile's website have been down for most of the day today. The exact nature of the breach is unclear, but the alleged hackers say they "have everything, their databases, confidential [sic] documents, scripts and programs from their servers, financial documents up to 2009." They go on to say that they've been in touch with the carrier's competitors trying to sell the data, but have (thankfully) been turned away, so now they're looking to hawk it to the highest bidder. If this is legit, we can't imagine that trying to sell the data in a public forum is the wisest plan -- but then again, we're not criminal masterminds, so maybe this is standard operating procedure. Here's hoping they're brought down quickly and T-Mob gets to the bottom of the breach.
Update: We've gotten an official comment from T-Mobile, and in brief, they're actively looking into the claim but can't confirm or deny whether it's actually happened. "The protection of our customers' information, and the safety and security of our systems, is absolutely paramount at T-Mobile. Regarding the recent claim, we are fully investigating the matter. As is our standard practice, if there is any evidence that customer information has been compromised, we would inform those affected as soon as possible."