It would be simple enough to rely on resource hashes to not actually contact the sources of files and then to skip or approve seeking hashes you can't get from your preferred shared caches. Thus a unique file gets ignored by the most anonymity concious.

I think there is a chicken and egg here combined with IP incentives to not fix how web browsers work.

I hoped the great firewall would have accidentally fixed this by making it preferable to refer to hashes that can be found in peer caches irregardless of CDN status.