AT&T is setting up an enormous network free to its subscribers in New York City's Times Square: The Wall Street Journal quotes AT&T's NY network head as stating this is explicitly to offload data. AT&T had said a year ago that it was considering large-scale hotzones for this purpose.
I've been baffled that the company didn't spend a few tens of millions of dollars in its troubled areas (San Francisco and New York City, notably) for Wi-Fi. The Journal notes that this is a pilot test, and AT&T may install similar networks in one to three other cities.
AT&T already operates 21,000 hotspots, and the iPhone, 3G iPad with active AT&T service, and some other smartphone models actively switch to Wi-Fi for data when in range of any AT&T-run location.
AT&T gives away Wi-Fi at its hotspots to 32m customers, including smartphone, laptop mobile broadband, DSL, fiber, and business customers.