I don't want to sound like a snob, but I've never really gotten the idea of having a song as a ring tone on my cell. It just seems obnoxious to me. But to each his own. It's mindless fun and generally doesn't hurt anyone (except for innocent bystanders who happen to be unexpectedly bombarded at high levels by "Umbrealla" when some jackass won't silence their ringer).
However, David Pogue of the New York Times sees a more sinister scheme at work, perpetrated by the music industry. I find his rationale convincing.
And, no, I'm not bitter because my sister made her ringtone for me the main theme from, "The Good, the Bad, and the Ugly".