It takes a bit of digging to get to the original source of the story, but it was The Consumerist who first reported on, err, reports from its readers that you could no longer order an iPhone online in NYC. The Consumerist contacted AT&T, and they were told that "the phone is not offered [...] because New York is not ready for the iPhone". They added that New York does not have "enough towers to handle the phone".
It is no secret that iPhone owners tend to consume more mobile data than other smartphone users (although Android owners probably aren't lagging behind), and with the iPhone being more popular than god, the poor AT&T network can't seem to handle the load. Since New York City has a population of 8.3 million in a tightly packed space, you can see how AT&T's network has to bear quite a load.
AT&T, by the way, changed its tune later during the day, when the news had hit the blogosphere hard. To CNet, AT&T stated that this was a routine thing. "We periodically modify our promotions and distribution channels," said Fletcher Cook, an AT&T spokesman, to CNet.
Just in case you can't feel the PR panic going through AT&T at that point, yet another AT&T person, a customer support representative, talked to Gearlog, and stated something completely different. He explained online sales were halted due to "increased fraudulent activity in that area when ordering the iPhone".
All is well, though, as AT&T has already resumed online sales of the iPhone in NYC. After a day of reading nothing but rehashes of this story, with update after update, it's good to hear the diversely unified people of New York City can once again be good little consumers. They had me seriously worried there for a second.