Not everyone would agree on that. Expecially those taking advantage of any of the 100 or so mods out for phpbb.
VBulletin is great and so is IPB, but PHPBB is the winner for me because of it being open source and having an extremely active development community. I've been a fan since phpbb has come out and it can handle any amount of forum users. Currently I believe that it has the largest forum community at phpbb.com
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