Washington, D.C. is suing AT&T because some customers who buy its prepaid calling cards don't always use up all the minutes. The city isn't suing on behalf of the customers, of course (though even that would be sort of silly). It's suing on the notion that when a customer doesn't use up all of a product or service they purchase, the remainder belongs to the government. So they want the company to pay what the minutes are worth to the D.C. government, where they might be better used on, oh I don't know, maybe to pay overtime for Mayor Adrian Fenty's mountain bike detail.
Next up, D.C. sues Burger King for stray fries that go uneaten after falling to the bottom of the drive-thru bag.