I used to frown on this, but after a lot of my favorite classic rock artists/bands had done it, I had to throw in the towel. I mean - Hendrix, The Beatles, Led Zeppelin...? If I had stood by the position I held as a teenager on artistic integrity, I'd have to deny myself a lot of great music. And then I'd be an idiot. Or one of Fugazi's biggest fans.
Also, there's the downloading issue. It's a neverending debate, but I think it's probably true that artists have lost money over the years due to illegal downloads. Whether that's a big issue or a small one, if artists can recover some losses by making television commercials, I guess it's worth the heartburn that you get when you catch one of these ads as you're channel surfing.
I should admit that, although I thought that I was learning to live with all of this 'selling out' shit, I was still a little bit pissed and pretty surprised when I heard a new Wilco song used in a freakin' car commercial. But, on the other hand, this is the same band that sent out a "Modest Proposal" in their newsletter asking people to buy Sky Blue Sky (a great album, by the way). I think that's admirable enough to give them a pass for selling some songs to Volkswagen.