Formal study: How many points networks share

[Sean Donelan <sean () donelan com>]

After the thread a couple of weeks ago on how many nexuses are needed
for the Internet to work, the MIB (actually a woman, but that's a different
thread) asked if there were any formal studies.

Have any providers done a formal study of how many points they share
in common with other networks?  I know most providers consider their
competition, if nothing else for how peering will be done.  There
seems to be a tremendous amount of overlap between networks.  Almost
every major network map looks identical.  And there are some third-party
consultants selling network maps.  But I was wondering if anyone had
a formal study from "the horses mouth."