Radio used to be the main way you'd discover new music in the days before the Internet. Sometimes I'd read about a band in a music magazine that either an artist I liked was influenced by or into and seek them out, but more often than not, it was constantly listening to various local radio stations that made my record collection grow by leaps and bounds.
I remember the first time I heard a rock song being used to advertise a product. I think it was the Who and I was mortified. I thought like so many did, "What a sellout." Mind you this was back when the mindset was classic rock was iconic and had to be preserved in its purest form. Some years later, Volkswagen was advertising a new car and this really beautiful, moody song was used. I was hooked. It took some time to discover it was Nick Drake. I immediately went out to buy the CD. Similar scenarios followed and my thoughts on it have changed completely.
Though the business of using artists' music in commercials goes back to the early days of rock and roll, it's been in more recent years (remember Moby made all of his songs on Play available for use in commercials) that it's been much more widespread. Given the fact that most commercial radio only plays the "hits" and video music channels are more about reality shows than videos, it's become a viable marketing tool for discovering new as well as established artists. Artists and record label execs are more inclined to push the music in a commercial or even a television soundtrack. Some of the more established artists such as Beyonce will actually make an appearance in the ad (American Express).
I can't say it makes me purchase the products the songs are being used for, but I'm all for discovering new music