I know the guys at SimpleFeed who are turning RSS into a targeted marketing channel.
Theoretically this is a pure channel because users "opt in" -- nobody has to read an RSS feed. It remains to be seen exactly how the ads are spliced into the feed stream such that I can opt in or out based on keywords, criteria, etc.
I think people wouldn't mind seeing advertising as corollary effects of reading content if the ads truly were targeted to them. "I'm kind of looking for a car, so if you serve me SUV ads in the $20,000-$30,000 range, that would be cool with me."