Currently, roughly a quarter of the threads on the front page of Spam are by you, and most of them contain little to no content or anything discussion-inducing. Kaga is wrong - activity for its own sake isn't enough. I could post a hundred threads with simply the word "The." as the OP and it wouldn't do anything. What's needed is content that prompt discussion, debate, drama, or further production of content. Look at the post above by Vordak. It's not contributing or prompting of discussion, it is a mindless nothing. When the majority of threads or posts are simply people writing their thoughts down, discordant or disconnected from the topic at hand or the potential for further conversation, inevitably you end up with a dying forum. Posts have to be made with the intent and mindset of connection with other posts and threads and Spam members - not isolated things, made for their own sake, a thought on the behalf of the poster with no enticement for others to join in, comment, or discuss.
This isn't aimed at you specifically - currently lots of people are guilty of this, myself included at times.
EDIT: Kaga's right about one thing, though - it was active last night. Why? Look at the threads made, those that encouraged that activity and discussion and joking and reminiscing and whatever. They asked for participation and they had actual content in them that people could engage with.