Forums did more than exist-- they were massively popular. Sure, I don't remember a forum with 1 billion members, but I'm still boggled at the colossal output of some of them. I remember pretty niche topics still with large, competing boards and real-life meetups... all before Zuckerberg even hit puberty. I think the author's point is that the web didn't just magically come alive in 2004, and this is more than true.