AHA! I’ve got an excellent idea about where to put advertising.
Check out this page where I’ve encoded some ambisonic material as streaming multi-channel AAC files.
Those files are being played back in an MP4 container. The MP4 container can also contain video.
What if that video contained advertising? This would mean that anytime anyone clicks on ‘play’ they would get the full surround sound experience, entirely uninterrupted… but they’d also get a bit of video advertising. The main point being that this video advertising would not interfere whatsoever with the audio content. But everytime someone listened to the audio content, they would see some advertising messages.
I think this would also be easy (technically) to implement.