They've had all sorts of problems with not having enough capacity to handle all of the iPhones in NYC. They have stopped selling iPhones for extended amounts of times to try to cope with it.
There should be an iPhone on Verizon within the next six months, according to engadget.
She wasn't necessarily on the ATT network though. Her iPhone is from an overseas carrier so she could have ended up connecting to TMobile or something instead when she turned on her phone and connected as a "roamer". ATT's problem sounds like lack of network capacity for the demand they created for themselves. I expect that the problem wasn't only evident on iPhones, but was probably CAUSED by the huge influx of iPhones...no?