Worse, the current technology used at the exchange points could encourage abuse. What is to stop anyone connected to an exchange from simply dumping packets anonymously at the link level into the various inter-exchange providers' routers and getting free transit?
Transit, to work, has to be bi-directional. Even if you can dump packets into another provider's network without peering with them, they won't hear your route announcements directly unless you do. And most providers out there insist on next-hop-selfing in both directions...
Yes, there are many people who do this. I know of a few who point sprint traffic to sprints MAE-East router and are not peering with sprint, but I don't see that as a encouraged abuse. That is steeling, and providers should not do it. If people want sprint to peer then build a full DS3 network and connect to every major NAP at DS3 ore more and I bet they will peer.
Even those who have steeled themselves to spend the $$$ to build the infrastructure needed may find that Sprint still won't (hasn't) peer(ed) with them. At least that's the claim.
Nathan Stratton CEO, NetRail, Inc. Tracking the future today!
Avi