AT&T claims that because Google blocks certain numbers from association with its Google Voice service, it violates net neutrality principles. [NYT] It's all about fees at the back end: poky local telcos scam the big carriers on connection charges. But whereas big carriers are forced to allow the connections, Google Voice is not.
The flaw in the argument is, of course, that Google Voice isn't a telco. It's a new application of existing technology that supercedes the business model that telcos rely on. Among other things, Google Voice makes it obvious that the services carriers charge for are worthless, and that bandwidth is their only real product.