1. There are two different standards in play for cellular service in the US. The GSM standard (which happens to be the one generally adopted in the rest of the world) is what AT&T and T-Mobile use. Nobody else in the US really uses it. Instead, companies like Verizon, US Cellular and Sprint are all on the CDMA standard instead. GSM signals are weaker and have more problems penetrating buildings, so that automatically gives CDMA carriers perceived "better service", without them spending a dime of extra money on infrastructure improvements.
2. We *all* know AT&T sucks, but it's also very likely true that ANYONE who agreed to an exclusive iPhone deal like AT&T did would suffer the same fate. Since the iPhone offered a better web browsing experience, a big screen compared to most other phones, longer battery life than most (allowing more Internet usage without worrying about running down the battery) and ability to download music and applications straight to the phone from over the air - it all adds up to it being a big "data hog" on the network. It's quite likely that at first, AT&T had no idea what to expect as far as all this usage it generated. (Remember, it was no "sure thing" the iPhone would even be very successful at that time.... and companies like Microsoft were predicting it'd be dead in a year.) They didn't even HAVE the app store ready yet at launch, either. Now that AT&T knows what the situation is, they've still only had maybe 2 years or so to build out the infrastructure to handle it. Meanwhile, iPhones are advancing too, with the 3GS series able to download at twice the speed of previous models!
