A possible solution: a command that would retrieve from all LISTSERVs any
id from your node, and what list they are on... then you could compare
the returned list to your list of deleted userids and issue the necessary
DELETES.  This would be a lot less traffic than sending (say) 1,649
delete-if-you-find-it commands to all the servers.
 Of course, this works best at LISTSERV sites, but a site without a LISTSERV
could use the same methodology as long as they had a LISTSERV postmaster
issue the DELETE commands.
 If that makes any sense...
/jenny