I found mention of this apparently infamous O'Reilly banner ad when flipping through my recently purchased copy of Programming Python. The ad is hilarious, and apparently pissed off enough Perl zombies to garner an apology from O'Reilly.

The thread on usenet re discovery of the ad (this link doesn't work any more and I can't find the original discussion on google)

The thread with O'Reilly's apology (this link doesn't work any more and I can't find the original discussion on google)

Here's the apologetic posting from O'Reilly (found in the above thread):

Hello all,

I'm Allen Noren, managing editor of the O'Reilly Web sites. Tim forwarded
me email from each of you about the Python ad on Slashdot. I want you to
know that I am responsible for the ad. and that it is not part of a
corporate strategy to fan the Perl/Python religious wars. On the contrary,
it was simply an attempt to instill some levity onto those flames as we
introduced an excellent new book. Set in the context of Slashdot I thought
people would get the joke. Of course O'Reilly is not dissing Perl or
promoting Python over Perl. We don't diss anyone or their operating systems
or their preferred language. I'm sorry if it was taken that way.

Thanks for taking the time to read this and for voicing your concerns.

--Allen