When Verizon bought Alltel, it became the biggest carrier in the US, with 83.7 million customers. Two years later, it has 94.1 million customers. And as of today, AT&T is number one again, with 95.5 million customers. Why? The iPhone. Updated.
(Update 2: The earnings release doesn't make this totally clear, referring to "95.5 million subscribers," but if you break down the numbers down further, it's 86.2 million excluding "connected devices" like the Nook or Kindle with AT&T 3G. Which is the actual number to compare to Verizon's 94.1 million. So, not the biggest. Point remains that iPhone was a huge driver of postpaid wireless subscribers who're new customers to AT&T.)
Not to put too fine a point on it, but a ton of AT&T's subscriber growth has been the iPhone. This quarter, 20-25 percent of the iPhones sold were to new customers—so around a million new customers came aboard with the iPhone. (Update: The million new iPhone customers were also offsetting people who left, hence the stat AT&T added only a net of 400,000 post-paid subscribers this quarter. Put another way, as AT&T explained it to me, they had 2.7 million gross sales to new postpaid customers. So nearly 40 percent of their sales to new postpaid customers were iPhones. They just lost a bunch of postpaid customers as well, hence a net gain of only 400,000 post-paid customers.)
Last quarter, nearly 25 percent of the 5.2 million iPhone activations were new AT&T customers—1.3 million, to be precise. And they added 2.6 million subscribers. Or a year ago, when AT&T added 2.7 million customers, over a third of the 3.1 million iPhones they activated were new customers—more than a million. You can see it again and again as you dive back into their earnings and subscriber numbers. (This, in case you are wondering, is why even Verizon, with its Mighty Network, wanted the iPhone so badly.)
AT&T will totally keep making buckets of money selling bushels of phones and connected devices just like they're doing right now, even when the iPhone is no longer its exclusive baby. But they might not be the biggest carrier in the country for that much longer, so they should enjoy it while it lasts. (This might be why they didn't trumpet it too loudly. Which is to say, not at all.)
P.S.: AT&T, how about those rollover bytes? Eh? Eh? [AT&T]