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Yeah, Wikipedia likes to present itself as some kind of generous charity but there are enormous motivations to control the content and the politics of editing it are highly charged politically. It's not just charitable volunteers, there are plenty of motivations to be the one who gets to make the edits. 
So many topics get deleted from Wikipedia. Political figures are deleted, military related articles disappear, articles about toxic dumping, industry scandals. There are plenty of reasons why many people are eager to edit Wikipedia that don't require being paid for it. And it's like Reddit in the sense that people want to build up good credit in some neutral topics in order to cash that in later when the controversial stuff comes up.
Holy crap there is already a Wikipedia article about the earthquake, and it's huge!
Wikipedians are insane >

They are those people that would have been scribes and chroniclers in the past. They would have lived their days recording censuses, documenting significant events in a kingdom, or record the lives of great individuals. To them information is something that needs to be recorded accurately as possible and done as quickly as one can do so. In a weird way they do the world a service by being ready to jump in and add such information at a moments notice. >

Most are anonymous and not all do it for free. There are hints of various governments and corporations "helping" edit Wikipedia for example. Wikipedia itself has an article on that with examples.