A lot like today's blogs.
One of the more prolific posters (and I can't for the life of me remember his pseudonym) turned out to be Tom Messner, who was one of the founders of the agency now known as Euro. I was junior enough at that point to have responded something like "you mean THAT Tom Messner" when he told me who he was. (There were actually a number of well-known ad creatives on that board, but that's another story.)
Anyway, Messner wrote a column in today's Adweek about ad blogos. It's worth reading because his take is always entertaining and because it's interesting to see an outsider's view of something you're quite familiar with. (Okay, it's also worth reading because one of the 5 or 6 blogs he mentions is mine. And damned if I wasn't thrilled about that.)
Read it here. (LINK FIXED)
My only complaint is that the Adweek techs who posted it didn't include links to the various blogs he references. That would have increased usability. Not to mention the amount of traffic to my site ;)