Originally Posted by Artashes
I think that if you moderate the forum proactively, you shouldn't have any problems. The only thing to remember is that Google/Microsoft search bots are constantly present on your site, so if they pick up links with bad rep from time to time before you have the chance to remove them, I don't know how that might affect your own site ranking.
I thought about that, but then I don't know how that might affect site ranking after Google checks back later to see that the link that was there has now gone because a Moderator has removed it. They must take stuff like that into account. They'd be pretty stupid if they didn't.
But I agree in that it could be possible to have an adverse effect temporarily. I'm leaning more towards that links probably don't affect SERPs for a week or two for the reasons I mentioned above. I'd like to think they have an algorithm for that to take it into account. They're well aware that a lot of websites/blogs/forums need to be moderated and links slip through.
I think as long as Mods remove them within a reasonable time then it should be fine. If one did get through that was very bad then Google would notify you about it at some point and then you could remove it manually.
Keep in mind that it's also good to link to other authoritative pages by dofollow. If you nofollow everything including links to well-known trusted sites then that may not help either.
I think no one other than Google knows the true answers to this, but I don't think it makes a major difference eitherway for the reasons I mentioned i.e using nofollow or dofollow both have their pros and cons but the end result will probably be the same.
Ps thanks for the email, Art.