This guy made it into the Technorati Top 100 with his “art of getting backlinks” site —”I have just finished working on my new tool - The Forum Register. Really it's a forum register - list of 5000 working PHPbb forums, and a forum registerer - tool that automatically sings up to those 5000 forums. As you know - registering on a PHPbb forum gives you a backlink - like this one. It's a legitimate, decent backlink.”
It seems necessary for phpBB to nofollow those backlinks.
Phillips —”Anyone want to rate this on the SEO hat colors range from Dark Inky Black Hat SEO to Luminescent Pearly White Hat SEO?”