Wikipedia @ 20

Wikipedia's first twenty years: how what began as an experiment in collaboration became the world's most popular reference work. We have been looking things up in Wikipedia for twenty years. What began almost by accident--a wiki attached to an nascent online encyclopedia--has become the world's most popular reference work. Regarded at first as the scholarly equivalent of a Big Mac, Wikipedia is now known for its reliable sourcing and as a bastion of (mostly) reasoned interaction. How has Wikiped