The main difference between music feeds and radio is not the absence of DJ, nor the absence of professional scheduling.
It is about permission. Permission to interrupt.
Advertising business model has been built for ages on interruption. Interrupted programs, interrupted flow of pages, advertising business never requested any permission from the end user.
Things changed with the web.
Do you know that most educated users will NEVER see those ads on your website ? They use adblockers. Those little plugins are available for free, constantly updated, and they simply block each and every banner, square or skycraper they detect. It’s just like those “no ads” stickers on your mailbox, except that it works :-)
An iPod is the same. A music feed (disorganized but instantely controlable) without any interruption.
How do we compete with that ?