Observations on greylisting (I get no spam any more)

[Daniel Webb <lists@danielwebb.us>]

I have been using the greylistd Debian package by Tor Slettnes for well over a
year now, and have found something quite astonishing: when I started using
greylistd, I received around 30-50 spams a day.  I installed greylistd and it
cut that by about 80%, which is similar to reports by others.  In the last
several months, it occurred to me that I don't get many spams at all any more,
so I turned off greylistd.  I receive almost no spam at all now.  Has spam
drastically fallen in the last year?  One person I know said they get about
the same as last year.  Is it because the spammers are treating the SMTP "try
again later" code the same as a bounce and remove me from their lists?

Believe me, I'm not complaining, but what the heck is up?

Daniel