Why wiki works

Arguments

Any and all information can be deleted by anyone. Wiki pages represent nothing but discussion and consensus because it's much easier to delete flames, spam and trivia than to indulge them. What remains is naturally meaningful. Probably.
wiki is not wysiwyg. It's an intelligence test of sorts to be able to edit a wiki page. It's not rocket science, but it doesn't appeal to the TV watchers. If it doesn't appeal, they don't participate, which leaves those of us who read and write to get on with rational discourse.
wiki is far from real time. Folk have time to think, often days or weeks, before they follow up some wiki page. So what people write is well-considered.
wiki participants are, by nature, a pedantic, ornery, and unreasonable bunch. So there's a camaraderie here we seldom see outside of our professional contacts.