AT&T is likely just throwing their hat in to diversify a bit after losing iPhone exclusivity. They want to do all they can to keep their smartphone levels at their current percentage, since it's leads to more profits then non smartphone marketshare. Had Nokia and AT&T announced this a year or two ago, I would have seen it as a more serious effort.

In the end, Nokia let the North American market slip away long ago before consumer smartphones were popular. In not reclaiming that market space, they let 4 American companies come along and just own the consumer space (Apple, Google, Palm and Microsoft). Even the Canadian based RIM did well in some part of the consumer market, due to their brand awareness in the corporate world.

It's been interesting to see the shift over the past many years in the mobile space. American companies contributed very little to the initial mobile phone rush, but have come back strong in the era of consumer smartphones. Enough that the rest of the world is also enjoying the products designed here, instead of looking at them as behind what people had access to overseas. Look at the popularity of the iPhone in Japan for example, a market well known for it's national pride in buying locally designed products.