automatic DB cleanup proposal

I think the base principles behind cleanups are great, and I intend proposing
APNIC explore a similar course of action to the manual sweep.

I am worried that there may be *external* referencees to objects, and while
we have no 'contractual' obligation it might not be nice to do this
to people without some engagement but I expect most people would welcome
losing a path to spam.

As to automatic sweeping, I think there are problems with link counting
which are similar to those we've faced in discussing cross-database linkage
and references. Too many risks of the link count getting out of whack.

I think you could use it as a guide to a sweep, but not as a determinant
without some review and other checks. Eg to trigger more exhaustive checks
to see if there are are references in twisty ways.

cheers
	-George