The Atlantic has the best article I’ve seen on the phenomenon that is Wikipedia. It’s a really detailed and interesting history of why and how it came about. I like this bit about why people contribute:
“Imagine that you happen upon your pet subject, or perhaps even look it up to see how it’s being treated. And what do you find? Well, this date is wrong, that characterization is poor, and a word is mispelled. You click the ‘edit’ tab and make the corrections, and you’ve just contributed to the progress of human knowledge. All in under five minutes, and at no cost.”
There’s also an interview with the author of the article on the Atlantic website which goes more into the different types of people who become wikipedians.