If you're a US Mobile Phone subscriber, you've undoubtedly heard plans advertised "free in-network calling." All the major carriers have it. T-Mobile and Alltel take it a step further and permit you to call a certain number of people for free regardless of the network.

The New York Times has a piece on how these in-network plans actually impact how people socialize-or don't. When you can call someone without cost, you are not motivated by the economics of the situation. When it costs real money to make that call, it appears some don't.

As someone who grew up back in the days when long distance on landlines was expensive, I can certainly understand the mindset. And those overage charges that the mobile carriers charge for going over your minute allotment are worse than what we paid back then. And it's not like the carriers go out of their way to let you know you're about to hit those nasty overage charges, either.

One of my friends actually maintains two mobile phones to resolve this issue. One is a typical post-paid Verizon account. The other is a pre-paid phone with AT&T that uses one of their pay-as-you-go plans that includes unlimited free in-network calling as part of the deal. He can call his friends on AT&T and Verizon-using different phones, of course-but not be "put off" by the whole "you're on the wrong network" thing.

What do you think about all this? Leave your thoughts in the comments.