Thinking about specific problems with sitefinder, here's a mail loss scenario: A site (a.net) is using a server in a different domain (b.net) as its backup MX. That server's domain expires and goes into the redemption grace period, or does not have any explicit name servers listed in the TLD zone for some other reason.
Image a.net's mail server is unreachable for a short period of time, because of maintenance. In the pre-Sitefinder world, e-mail for a.net would be queued up, since the backup MX can't be found. In the world according to Sitefinder, e-mail to a.net is directed to Verisign's "Snubby Mail Rejector Daemon", and (to the extent that Snubby works as intended) discarded.
