The other day I noted I'd implemented a simple change to my server logging to filter referral spam.  This change is a great source of satisfaction; I love viewing my referral logs and knowing every single entry is legitimate.  But this morning I noticed something which amazed me - all through last night I'd been receiving referral spam hits from URLs which are not on the air!  The essence of my filter is that it explicitly checks referrals by retrieving the page which allegedly links to my site.  These referers made it through because I don't eliminate invalid URLs; I figured what would be the point?  So here we have a referral spammer who was successful because of incompetance.  Of course they were only successful in defeating my filter; the sites they're advertising don't exist, so there really is no point.  Man.