First, there's no evident antitrust problem here. A violation of the Sherman Act requires either monopolization (distinguishable from monopoly, particularly as the term is commonly used, but definitely not in play here) or an anticompetitive agreement between horizontally aligned entities. Mere unilateral decisions to not carry this service, even though they are anticompetitive, are not illegal. This is akin to airlines raising their prices on particular market segments because others have raised their prices. The net effect is anticompetitive, but lacks the agreement required to prove an antitrust violation.
Having said that, though, the result is very unfortunate. I know Sprint has refused to carry some beautiful Samsung phones (that were, in fact, made just for Sprint) because of features that were not specific to their Vision service. They all use some lock-in tactics that are frustrating to consumers and refusing to give the go ahead to Motorola's iTunes phone is probably such an example. I personally don't think too many people want to purchase music through their phone, but they would love to interface with the computer and play Apple's AAC files on non-iPod devices. Hopefully, at least one carrier will step up to the plate.
