Effective September 6th, new AT&T customers (and those upgrading, for that matter) will have a mandatory, monthly fee added to their account should they purchase a smartphone: the $30 data plan.  According to AT&T, the change is primarily intended to cut down on potentially high bills as a result of pay-per-use data:

"Smartphone users tend to consume a higher amount of data services, like advanced e-mail, mobile Web, applications and more. Being able to take full advantage of these features without having to worry about a fluctuating or unusually high bill generally leads to greater customer satisfaction, so effective Sept. 6, smartphone customers will need to subscribe to a data plan, as the vast majority of customers already do."

Those currently without a data plan won't be required to modify their services until the time comes to purchase a new smartphone.  While I'm generally opposed to a carrier forcing additional chargers on a customer when he/she may or may not want or need them, I can see where AT&T is coming from.  It saves the "how did my bill turn into $1,300?!?" customer service calls.  As long as the data plan isn't tied to the two-year agreement (so I can switch back to a normal phone and ditch the smartphone plan at my choosing without fees), it's a reasonable proposition.

Source: PhoneScoop