As a consequence of Wikipedia's fame and scale, it's where people put knowledge when they don't know where it should go. This perception is actually at odds with the project's goals: to create a tertiary reference for information and viewpoints published elsewhere. Problem is, they've ended up with more information on Pokemon or Star Trek than, say, Civil Rights or the Second World War -- and that's not how they wanted it.
Like the protagonist of many a Zen koan, upon reading these words, I became Enlightened.
There are plenty of specialized pop-culture Wikis out there, and a lot of them use the same open-source wiki software created for Wikipedia, and offered freely by the Foundation.
Most people aren't aware of these specialized Wikis. When they want to find details on "City on the Edge of Forever", they don't go to Memory Alpha -- they go to Wikipedia. If they don't find what they're looking for there, the add the page.
And then the Notability Police get cranky.*
*Or they should, if they enforced those standards consistently.
My proposed solution? Distributed Wikis with a central search. Tweak the MediaWiki database code so that the owners of the specialized Wikis can "opt in" to the main Wikipedia search engine, and searches will return appopriate entries from any participating site using the MediaWiki code. Wanna find exhaustive detail on how a lightsabre works? Boom, you get links to two or three Star Wars wikis, a general sci fi wiki, and a Mad Science wiki. You get more information, Wikipedia doesn't have to suffer the embarassment of having a longer entry about lightsabres than they have about the printing press, and it's almost entirely transparent.
This owes something to the idea that Linden Labs and a few other virtual world creators are pushing, of allowing characters from one virtual reality to cross over into others transparently.
Ironically, the TV Tropes Wiki doesn't use MediaWiki, so the source that inspired this idea would be left out, barring cooperation between the WMF and whoever codes their database software.
Now, I just need to figure out where to send this idea. Or learn enough MySQL to start hashing it out myself...