[JoshTriplett]

For more information on that, look for the term "peering", or potentially "transit". People who want to get bits from one place to another on the Internet need to peer (directly or indirectly) with people who have fiber strung all over the world.

Peering arrangements normally involve some evaluation of whether the arrangement benefits both sides or just one. If you have things that an ISP's customers want, then theoretically that ISP wants to peer with you to improve latency and bandwidth...but in practice, if that ISP's customers will find an indirect peering through some other network provider good enough, and the difference isn't particularly noticeable, then that ISP doesn't necessarily have an incentive to make it better.