In a virtual community, CommunityLore is community knowledge - it's shared, but not very visible from outside. It's things people know but don't write out loud. It can be personal (on user's life, tastes …) information that's been hinted at at various places, various people's reaction to conflict, etc.
Now, debate forums do create information - but it's mostly implicit information - everybody bounces a topic around, than it's rolled back in the archives, and almost nobody reads it any more. A comunity that debates, say, on gun rights, may have amassed a vast store of knowledge, but it doesn't profit much to exterior members.
Some knowledge may be better left implicit - stuff everybody knows, but bringing it to the light may cause problems. That's the idea of ForgiveAndForget (and that's why ForgiveAndForget is much more meaningful on wikis - on forums (and much more on irc !), everything is forgotten. Similarly, the MeatballWiki community shares much more knowledge about (unnamed disruptive person) than you can get just by reading the wiki.
Contrast with ExplicitInformation.
See also: MeatBall:CommunityLore.
ImplicitInformation? is frequently communicated in programming languages. If I say "foo = 4;" in a method definition, but I didn't declare foo in the method, then it's implied that foo is either an instance variable, or a global variable.
But we'd never call it CommunityLore.
OK, page renamed (but not reworked)