I'm just installing a new mail server, using Exim 4 and the sa-exim Debian package. Part of the configuration uses Teergrubing (or tarpitting), and while it sounds like a great idea in theory, I also understand that a lot of spammers these days make it pointless. They either get around this problem by using huge botnets (which have other advantages for the spammer) or they just end the SMTP transaction immediately after sending the DATA portion of the message.
But my question is really "is this of enough use to actually foil most spammers?" I know that there's still lots of stupid spammers out there who use unsophisticated methods to send their junk. I'm just wondering whether tarpitting is worth it or not.