WebmasterWorld have only one forum for paid members, it's a "Supporters forum".
This thread posted in public accessed area:
http://www.webmasterworld.com/forum30/30575.htm
and counts over 20 pages. I juct can't post it all here ;-)
In short: Google start to penalize directories using overoprimization or reciprocal tricks. Also they implemented content duplicate filters and it's also against directories.