"It's sad that the Wikimedia foundation let the deletionnists destroy so much value in Wikipedia without providing an alternative (like dedicated community wikis)."
Partly because Wikia is a for-profit, extremely unethical company. They stuff more ads than content on their wikis, force established brands to move to .wikia subdomains, force awful design changes on their users, and they don't hesitate copying content from other wiki bases such as Gamepedia.
(ATA: I was an admin on WoWWiki, one of their largest wiki, when it was sold to Wikia. I kept in touch with Wikia employees since.)
This is why I tend to support wikis hosted elsewhere, or those that move away from Wikia. For example, the Bulbapedia site here is self hosted, and part of a Nintendo Independent Wiki Alliance that encourages people to leave Wikia and join their network to avoid just this sort of thing:
They still get the odd email from a delusional Wikia staffer trying to get one of their sites to become a Wikia site, but they immediately turn them down.
There have been so many exoduses off of Wikia from mid-sized wikis (let alone big ones like WoW Wiki). I'm one of them -- the Dungeons and Dragons Wiki. Around the time they stuffed that awful new skin onto everyone and told us that if we didn't like it, leave. We left. Deletionists ruined Wikipedia and greed ruined Wikia.
It was once a pretty good wiki farm, and I can't complain about the support. Then the skinpocalypse happened.
I understand this as an argument not to use Wikia, but not as an argument for why there is no other place on the whole wide Internet to host content besides Wikipedia itself.
New wikis are practically the hello-world project for every programming environment that can build a web app, so it's hard for me to understand what's so important about being hosted in Wikipedia, other than to ride on its SEO coat tails.
Why shouldn't Wikipedia be the place for all factual, verifiable, minimally notable information in the world, so long as it's properly organized?
Wikipedia is a long long way from that goal, even if we exclude fictional-universe nonsense. Pick nearly any historical subject; dozens of books filled with information translate to a few sparse Wikipedia articles. That's terrible.
Wikipedia is the place for all factual, verifiable, minimally notable information. When stuff gets rejected from WP, it's almost always because it fails one of those three simple tests.
For instance: someone downthread complained that WP was missing coverage of local bands and an interesting BBC documentary. The BBC documentary should be in Wikipedia, and if it isn't, it's probably because whoever wrote the stub article for it wrote it poorly; someone else should re-add it. But the local bands most likely fail both notability and verifiability: if nobody has written about them, (a) chances are they aren't notable, and (b) whatever is notable about them can't be tied to a specific reliable source, which would make a Wikipedia article about the band original research.
A really common place you run into trouble with Wikipedia is when your proposed article breaks new facts about its subject. That's not supposed to happen. Wikipedia is a tertiary source; if it makes a claim, that claim needs to be sourced from something else. "Original research" is a confusing term for this, but it makes a lot of sense once you grok it. From the perspective of an encyclopedia, there isn't much difference between someone's random harebrained theory about cold fusion and a discussion of the lineup of some New York hardcore band nobody's ever heard of outside of NYC.
I think you and I have argued about this before, but I've never understood why "verifiable" isn't the end of the criteria. If the accuracy of information is verifiable through the referenced reliable sources, why should anyone care whether that information is "notable" or not?
Wikipedia's definition of "notable" is simply "significant coverage in reliable sources that are independent of the subject". There isn't a lot of daylight between "notability" and "verifiability".
Well, the real point is "Why should they when somebody else can?" Especially since I don't strongly believe that Wikipedia will necessarily be "ad free" in, say, five or ten years. Time rolls on. Wikipedia should be focusing on making the best Wikipedia they can; let other focus on making the best community sites they can. We don't have to bundle everything into one organization.
Why should they, if Wikia does it?