ix's & prefix registration

to some extent, that would be a -very- nosy ixp.
  exchange operators often try to limit their liability
  by staying out of the relationships between peering
  partners that use the exchange fabric. simply managing
  the "common areas" has been considered enough of a task
  for the ixp. (common areas; e.g. the switch-fabric,
  possibly cross-connects, fabric support infrastructure etc.)