Thanks to customer outcry, Cingular Wireless has ended a program [subscription] where customers could access their information more easily. Between June 8th and 10th, you could access any Cingular customer's account info by providing just their phone number and zip code.
The available info--the plan, how many minutes remained, the last payment, and the outstanding balance--was available through the phone or Cingular's website.
You could also pay your bill with a previously used credit card, which could have led to customers' cards being charged without their authorization.