True, and it can work... As long as the ad spots are static and not dynamically placed.
Otherwise you could probably fingerprint ad spots and submit them into a shared database. Like musicbrainz. For dynamic blocking of static content. Acoustic ID is probably enough and it would work with podcasts too!
I hate ads so much, I would totally volunteer to make this my hobby.
Advertisement simply sucks and is offensive. There is nothing to respect about any of it. People will always find ways around.