For me I got two plugins to take care of forums. one is Xenutiles and XF Qaptcha . These two plugins pretty much covers it, now for those who bypasses these two plugins I would love to get another plugin who restrict users to post img and links before X posts. There is one addon available in RM but its kinda buggy so I have uninstalled it.
And for sneaky advertisers, I got very active staff and I do encourage users to report it.
What about you guys ?