Time for multiple carriers!
First, a vote casting - if I could get an iphone with verizon, I'd absolutely have one.
Second, I think the phenomanon they named, of imitators to the iphone establishing iphoneness as the ultimate, to be imitated phone, works towards multiple carriers. Imitators say (implicitly) that the iphone is the best, but also that it is now a category of phones, with second and third bests that you can settle for. When the iphone first came out, this wasn't the case - it was a category unto itself.
As it's own category, the single carrier model makes sense. If you buy into the new category, then it holds enormous power for you, because there is no substitute. Switching carriers, then, is clearly worthwhile. For ATT, the value of new customers, who will likely not switch long term for another phone, is immense, so apple can get more money out of them, and get nearly the market share.
But now, that isn't quite the same. There are imitators - sure, the iphone is the penultimate non-business smart phone, but there are other options. Now you must decide between compromising on phone or on carrier, and who knows how that will end up. It used to be that you had to compromise on the carrier (if ATT wasn't what you wanted), but that was dwarfed by the phone decision, between having it all with an iphone, or having a normal phone, AKA nothing.
So I say, multiple carriers! Plus, I want an iphone but live where I would never get a signal for it, anyway. So for me it is actually the inverse choice of the origional iphone - I must compromise on the phone, because otherwise I don't have the experience of having a functional cell phone.