If Apple includes a universal 3G chipset that can be use with any provider, then go for it. i have no problem with that and I can understand the benefits. Really I do, i did state that a few time.
But if Apple is going to use that as a way to get its laptop subsidized, it's more likely it will be restricted to specific network.
Dell has the same thing going for their minis, they are restricted to ATT networks only and it doesn't seem to be subsidized either. You pay to add it in, no option for anything else.
as long as it's optional then I don't see a problem.