Music Ally went through Apple's testimonial at the UK Copyright Tribunal's decision on online royalty rates, and discovered a quote from iTunes VP Eddie Cue:
The placement of third-party advertising at the start, end or during actual delivery of a Repertoire Work to a customer by way of a permanent download.
Sounds like ad-subsidized iTunes, doesn't it?
Tech Digest adds some observations:
Meanwhile, the QC overseeing the Tribunal decision, Judge Fysh, is quoted as saying "iTunes may well carry advertising in the future—hence their interest in these applications."
This is far from a secure thing, but it's clear Apple's thinking about it. [Tech Digest, thanks Stuart]