There is also the ability to "free" unused blocks (with CFA commands at least), maybe so they can be erased in the background, or freed from wear-leveling tracking. There is a commercial device-mapper plugin to force large physical sectors on devices that still use 512 byte logical sectors. Not much different than md-raid devices whose stripe width or stride is much like a large physical sector.

I agree that using routing information from the BGP routing system makes a lot of sense. Each ISP could give a feed of their routing table to their own customers, which may already contain tags or "community strings" which show what routes are internal, via settlement free "peering" at an Internet Exchange, or via paid transit (their upstream ISPs). The feed could give P2P and other clients information on the prefixes/routes that are "lower cost". The burden of all 269,000 prefixes could be lowered to say 10%by filtering out the ones that have no "discount" on their useage. One obvious use outside p2p/p4p is DNS. There are often "closer" or "farther" choices when given more than one DNS server to query, starting with the root-servers, yet they are normally queried at random. Bind8's sort-list feature could be re-activated, and fed a BGP table of "local" routes, giving quicker and more reliable DNS lookups everywhere.