He's got spammers forging messages "from" his domain, generating huge amounts of back-scatter (bounced messages and the like).

Same here, the double bounces are annoying (3740 bounces over the past 12 days). But what really gets to me is the fact that my domain got blacklisted about three times already, even though the Received: headers clearly show that the spam emails did not originate from or were relayed by any of my machines.

The worst of all was the father of a 5 year old that started filling my inbox with hatemail after his daughter got porn spam with a faked from address that made it look like it was coming from my domain.