On wikis, a lot of knowledge is explicit - at least, the important stuff. It’s easier to find what a wiki community thinks of, say, CreativeCommons than, say, an artist bulletin board, or slashdot commentors - even if it’s more on-topic over there !
Explicit information is more valuable where you have ContentOverCommunity.
Contrast with CommunityLore
The difference between explicit and implicit information is subtle … on a bulletin board, it can be the difference between a “sticky” topic and an ordinary one.