Chu said “With the combination of Android Market’s new app discovery features and a carrier-backed frictionless payment method, users will find it significantly easier to discover and purchase applications of their choice.”
Customers with AT&T Android devices just simply go to the app they want in the market and in the pulldown menu at payment they will find the option to bill their AT&T account directly. If you don’t call customer service to make sure your account can handle that type of payment.
Carrier billing is currently offered by T-Mobile in addition to AT&T and Google is hopeful that more carriers will partner with them for this type of billing.
Source: Android Developer’s Blog