We have learned that effective July 31, 2009, AT&T will be changing how they charge Data Pay Per Use. Currently, AT&T is charging $.01 per kilobyte of data. The new rate will change to $2 per megabyte or (if my math is correct) $.002 per kilobyte. The charge is rounded up (of course) so if you use 1.1 megabytes of data, you pay $4.

The new pricing is for new postpaid activations and existing postpaid customers who change their voice rate plan, downgrade from a Data MRC plan to the Pay Per Use plan, request the new rate, or request a data credit. The rate changes exclude Legacy Family Talk, Prepaid plans, Legacy Blue and Dobson plans, iPhone specific plans and all business plans except Business Talk and Pool Nation.

Granted if you're on an unlimited data plan this won't change anything for you.  This will help out AT&T customers who are already on a pay per use plan and might attract additional customers considering a data connection who simply want to explore the mobile data realm without committing to an unlimited plan.