You said: "That means when one neighbor sends traffic to another neighbor via the ISP, they both usually pay." This is true, if they are both customers of an I

You said: "That means when one neighbor sends traffic to another neighbor via the ISP, they both usually pay." This is true, if they are both customers of an ISP, and they are using that ISP to transit traffic to each other, they both pay. But if we have a lot of traffic destined for each other, it would make sense for us to peer and reduce our bandwidth costs from our upstream providers. DOCSIS only works in reverse if you are willing to install cable plant equipment at a customer site, which would mean a rack full of head-end gear at every house. Not feasible, and won't happen tomorrow. I used to handle BGP and peering for a tier 1 ISP and CLEC in the western US, so I've seen my fair share of peering agreements, and I've run my fair share of DS3, OC3 and OC12 circuits to peering locations. It sounds like you have a lot of credentials working for OpenDNS, so I don't mean to denigrate your experience, but OpenDNS seems more like a bandwidth customer and less like a provider/peer. I have a lot of experience with cable plant equipment because we provided cable modems and DOCSIS equipment to a lot of small business/enterprise customers in the late 90s/early 2000s.