Of course my argument holds up. It's true by definition. But remember, my first post said that I thought there was a stronger case for a GSM monopoly.
Look, the term "monopoly" is a pretty strong word, and it carries with it certain connotations that I don't think apply here. So if you want to use it in the strictest sense of "a market with only one seller" then I agree with you, but saying that "AT&T has a monopoly on GSM mobile coverage" has about as much weight as saying "Apple has a monopoly on iPods." Yeah, true, so what?
There are no other GSM providers of note which offer modern, up-to-date services (and handsets) and are a serious option now, besides ATT. I was snarky because I suspected obtuseness; I think that obtuseness has now been confirmed.