The AT&T vs. Google Voice debate has gotten much more interesting/entertaining, thanks to a letter from AT&T to the FCC, loudly trashing Google—and even the FCC themselves, for allowing Google to run rampant. There's some serious animosity here.
In the letter, AT&T outlines a lot of their specific problems not just with Google Voice but with what they see as lack of regulation of Google as a whole. Their first main point is that Google Voice isn't merely software (which wouldn't be regulated by the FCC), but seeing as how it connects calls between users, it should be seen (and regulated) in the same way as typical wireless carriers. They've asked for an FCC investigation of GV before, but now we're getting some more in-depth reasoning and, even better, some smack talk. The salient paragraph: