First ask yourself how many active forum members are available and making posts and what are the boards they like posting, signature campaign most times does not interfere with a members way of posting and for that, each and very time you see a particular board becoming more active than the other is because of the interest of the active forum members.

Fact check that gambling board is one of the most active board hee in the forum and there is also no doubt that most advertisings here on bitcointalk are all sponsored by gambling sites so that have been the normal order, it's all about the interest of each forum members.