I'm not sure where Dan stands on this, quite, but I much prefer "traditional" to "authentic."
Basically to me "traditional" means that there is a tradition to which the cook, dish, restaurant, or whatever adheres. If you want to say that you're serving "traditional" Mexican food, I don't have a problem with that -- but I would be somewhat nonplused if I asked you where in Mexico, or which tradition, and you had no idea what I meant. For example, I know that if you ask Rick Bayless this sort of question, you'd better be prepared for a very, very long answer, because he'd be delighted to tell you all about it. He's into this. Batali is too, for example, and so are many others.
To my ear, however, "traditional" differs from "authentic" in that it doesn't imply rightness or correctness. That's the part that drives me nuts about "authentic."
I suppose in what I wrote above, I kind of overstated the issue of racial bias, although I do think it's very real -- and not in any sense limited to food TV judges. I think it's become a constant issue in American food talk, and I think that's very unfortunate for a lot of reasons, not all of them having much to do with racial concerns.
One neat example for me is kaiseki, the ultra-refined cuisine of Kyoto. There is certainly a tradition of kaiseki, and a very complicated and debated one, with all kinds of varying strains. By one measure, it's some 4 centuries old; by another, it's less than 100 years old. Regardless, it's a complex tradition, and a vibrant, dynamic one as well. But by any reasonable measure there is no such thing as "authentic" kaiseki -- or alternatively, "authentic" kaiseki is so defined by the fact that it is served in Kyoto or its immediate surroundings and makes plausible claims to the tradition in question. "Authentic" kaiseki cannot exist outside Kyoto: that's meaningless. But you could certainly have a restaurant in Osaka, Tokyo, LA, New York, or Barcelona that goes to some lengths to serve traditional kaiseki, and then the question would be whether that was a good idea or well executed.