sell shell accounts?

o Given that each link is rather expensive, it behooves the
  NSP to try to avoid needlessly moving a packet back and
  forth across a DS-3 local loop just because my ATM
  provider can't provide me with any more PVCs.
  (Which was my major point, by the way.)

Interestingly enough, the NSPs I observe moving large amounts
of traffic around are set up in such a way that their routers
are generally colocated with carrier transmission gear, and
so there *is* no local loop to speak of, as an added cost to
an outside supplier.

There are issues involving intra-POP technology and the like, though,

Moreover, the other folks I observe moving large amounts of
traffic have no less than two local-loops built with maximal
redundancy in mind (different trenches to different facilities
and often using different local carriers), so it is much less
a question of moving traffic back and forth across the same DS3
local loop, but rather an extension of the intra-POP technology
problem faced by the folks with tight relationships with IXCs
and overseas equivalents.

Do you still see configuring up large numbers of PVCs to be an
advantage in these two cases?