  Since its inception six years ago, the online encyclopedia Wikipedia has
accumulated 6.40 million articles and 250 million edits, contributed in a
predominantly undirected and haphazard fashion by 5.77 million unvetted
volunteers. Despite the apparent lack of order, the 50 million edits by 4.8
million contributors to the 1.5 million articles in the English-language
Wikipedia follow strong certain overall regularities. We show that the
accretion of edits to an article is described by a simple stochastic mechanism,
resulting in a heavy tail of highly visible articles with a large number of
edits. We also demonstrate a crucial correlation between article quality and
number of edits, which validates Wikipedia as a successful collaborative
effort.
