Yes, that's exactly my point, Gede. Out of the box, forum software is not very spider friendly and the www.phpbb.com forum is right out of the box, so I'm not surprised their pages aren't well indexed. But as you yourself know, that is easily remedied.
phpbb.com was penalized by Google manually about 18 months ago... not because they were PR10 (at the time), but because they were PR10, and decided it would be a good idea to sell text links on their site and blatantly advertised they were selling them based on them being a PR10 site.
They wisely removed the thread after it happened, but it *was* here: http://www.phpbb.com/phpBB/viewtopic.php?f=14&t=151940 Which you can see a link to from Archive.org: http://web.archive.org/web/20031207025549/http://www.phpbb.com/
I assume it was this one? Well, I guess I don't get to see the thread but I did see this, referenced as "pricing structure":
Dunno, if this link selling was the case of a manual removal, could be. But to me it seems that sites like mine, also with a lot of footer links to their site, are sort of automaticly derived of transferring external pagerank. I don't sell textlinks, yes I have links to my own site... Or I am the victim of a manual penalty too. But I don't think I am famous enough for that.....