anyone have any tips to prevent forum spam?

[ZiNgA BuRgA]

Thanks for the compliment, but it's definitely not 100% accurate, or anywhere near really.
There isn't too much spam on these forums, possibly because I've blocked most Indian IPs from registering here, so there's only really a small sample, but on my main forum, it's failed to detect some, and has falsely detected legitimate posts.
This is primarily a link analysis tool, so it mainly flags posts containing lots of links.  The more conservative spammers, only putting in one link (or those that don't put in any) generally won't be picked up by this plugin.
It's not designed to pick up all spam, just make it slightly easier for the moderators by stopping the aggressive spammers.  Primarily, this tool assumes that the forum is being moderated well already.

The plugin can automatically unapprove threads/posts suspected of spam, but it's disabled by default and I won't enable it.  I prefer blocking the post itself, as it tells the user why the system doesn't like it.