I think it should be possible to build something akin to Tor (or even use the Tor protocol directly) that proxies requests and responses through intermediary no

I think it should be possible to build something akin to Tor (or even use the Tor protocol directly) that proxies requests and responses through intermediary nodes, so that the sender doesn't know who's the receiver and vice versa. But you're probably right in that this is a relevant problem, as IP addresses are considered PII (in Europe at least), so leaking them could be problematic. That said, as Netflix already has a contract with each of its subscribers it shouldn't be too difficult to modify it to accommodate that kind of data sharing. I imagine the real problem is ensuring streaming quality in such an infrastructure, as it's very hard to predict when a node will go down (e.g. user turns off laptop) or massively degrade in bandwidth (e.g. user starts downloading other content), and there's not much that customers hate more than interruptions when streaming movies (as you can probably attest firsthand). So given all these constraints it might be cheaper just using a CDN. Also, the bandwidth costs per customer probably make up a negligible share of overall costs (licensing is probably the biggest part) so it might not be worth optimizing this at all. I'd estimate that when I used Netflix I streamed maybe 20-30 movies / episodes per month (sometimes more), which would total at about 50-100 GB max (?) given the right encoding. For a company like Netflix that distributes probably petabytes of data a single GB should cost significantly less than 1 cent, so my bandwidth cost to Netflix would be between 0.5-1 $ per month (I even think it's much less probably).