I don't think anybody is complaining about paying for a data plan that you're using, which is how it appears some people here have interpreted this new policy. I took it to mean that AT&T will no longer allow you to buy any phone they consider to be a "smartphone" without paying for unlimited data @ $30/mo.
Since iPhone 3G, with iPhones at the very least AT&T has always had a policy that required you sign up for data if you bought an iPhone (you couldn't sign up for a voice-only plan and have data usage blocked and simply live off of WiFi), but it sounds like that policy wasn't enforced across-the-board with all of their smartphones. With this announcement, it simply sounds like they are standardizing this policy across-the-board.
For those that currently have smartphones that are not on a data plan, AT&T will not force them to sign up for one. But all new smartphone activations from Sept. 6th onward will be required to have one.
I can see why some people, who would like the benefits of having a combined phone/PDA but don't see themselves using cellular data at all, would be disappointed by this decision. The complaint is not that they were getting free data before somehow and now are being forced to pay for the data they use. It sounds like the complaint is that they will be required to buy a data package, even if they won't make use of it, if they activate a smartphone on AT&T's network.
-- Nathan