Wowpedia is, like Wikipedia, based on user contribution. I mostly use it to find out stuff about macros, rewards from a certain faction, or lore. The main point is, if no one contributes to it then it won't evolve.
Upon finding the information you needed on Wowhead, did you then create an article for it on Wowpedia? Probably not, which is why it's not there.
Edited, Dec 2nd 2010 5:16pm by Mazra
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Please "talk up" if your comprehension white-shifts. I will use simple-happy language-words to help you understand.