AT&T has confirmed the letter's authenticity. "We've just begun sending letters, emails, and text messages to a small number of smartphone customers who use their devices for tethering but aren't on our required tethering plan," spokesman . "Our goal here is fairness for all of our customers."

AT&T's clearly state that unofficial tethering apps aren't allowed, so the carrier isn't doing anything unethical. But I always out that charging customers to tether their phones while also capping their data is double-dipping. Customers should be able to use their data allotment however they please. So while I can't fault AT&T for upholding its terms of service, the threat letters .

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