I believe the Lakers forum used to be the most active at JBB, and had the most active posters, including Shapecity, Brian, heuvon, and Mamba, back when JBB used to be around.
All of the JBB threads were imported to S2.
Meanwhile, the Nets forum has the most post because some start threads, while others feed off of those threads by addressing the subject. Sometimes, we go completely off-topic, and that ends into a lengthy discussion and/or argument that takes many posts.
Also, we have things like the Haiku thread, Fantasy Basketball thread, and multiple game threads which include hundreds of replies.
Hell, the Lakers thread with the 7th most posts contains the same amount of posts as our 23rd biggest thread.