The truth is that Wikipedia reveals what is normally hidden in an encyclopedia: the countless decisions that lie behind each entry. The only difference is that in Wikipedia, the decision-making never stops and the debates are often robust to say the least.
[Encyclopædia Britannica] Editor-in-chief Dale Hoiberg is no less damning: "People write on things they're interested in, and so many subjects don't get covered; and news events get covered in great detail. The entry on Hurricane Frances is five times the length of that on Chinese art, and the entry on Coronation Street is twice as long as the article on Tony Blair."
Wikipedia's great for looking up characters in science-fiction universes, heavy-metal bands and internet protocols, and other areas of geek interest.
So it's kind of a like an open source uber-Jargon File (since the actual one, isn't...)
Something like that. Then again, it's not quite as bad as that caricature; today's featured front-page article was about Greco-Buddhism, the interplay of Hellenic and Buddhist influences in Greek kingdoms in Central Asia after Alexander the Great.
Is there a problem if wikipedia only details what people are interested in? Surey that's better than writing volumes about things that only a few people are into?
Part of the joy of an encylopedia is discovering things in it, Kae. If I'm interested in public-key cryptography, odds are I'll know everything the encyclopedia has to tell me already. The fun part is finding out new things I _didn't_ know before, or didn't even know I was interested in.
Recently, Edward Felton published a comparison of Wikipedia and Britannica in an attempt to determine which one was more complete. They concluded that on the topics they looked up, Wikipedia was better (http://www.freedom-to-tinker.com/archives/000675.html) - however, it was revealing that every topic they chose to research was technology related: public-key crypto, Microsoft anti-trust case, etc. Had they chosen to research, say, the history of Gibraltar, or D.H.Lawrence, I doubt Wikipedia would have had as great an advantage.