User blog comment:Cook Me Plox/What do you want to see from Wikia?/@comment-1427921-20111023113339/@comment-1025281-20111024082546

The reason why our (Avatar Wiki's) external forums were filled with spam was because they used phpBB's default CAPTCHA, which is widely regarded as absolutely useless. Eventually, a choice between getting rid of those forums and installing a half-decent CAPTCHA was given to the community, and consensus fell overwhelmingly in favour of getting rid of the forums. Users concluded that participating in forums that were on a different address altogether was just too hard.

I don't think that experience is applicable to this case. If Wikia were to reinstate their abandoned project of introducing phpBB forums, the fact that they share log-in with the rest of the wiki (and a CAPTCHA that doesn't happen to be useless) insures against spam. As log-in and domains are shared, the conclusion that users came to on Avatar Wiki would not be true, either.