I swiped this quote verbatim from Copyfight, since I can't improve upon it:

This has been around now for awhile in Britain, but AT&T Wireless is the first carrier in the US to offer Shazam's song identification service. If you hear a song you like (or don't like, as the case may be) but don't know who it's by, you can just dial #ID (or #43) on your cellphone, hold the phone near the speaker for at least 15 seconds, and then moments later you'll get a text message with the name of the song and the recording artist. They say they've got a million songs in the database, and that for right now you can try it out for free, though later it'll cost 99 cents a pop. (Engadget)
I'd be curious to know if/how AT&T is handling the copyright issues for this service. Are they instructing their customers to make digital retransmissions of copyrighted sound recordings? What about the "million songs" they have copied into their database? Is this infringement? Will the RIAA sue? Inquiring minds want to know...

Very often, I hear a song and love it, and don't know what it is. I am fully capable of remaining ignorant of song titles for years on end. So this is a service that speaks to me, and that would most likely result in me rushing out to buy the song. Based on past performance, I doubt the recording industry will see it that way.