Just saw this:
"What Motivates Wikipedians": review of a survey
<snip>
* Altruism and humanitarian concerns
* Responding to requests by friends or attempting to engage in an
activity viewed favorably by important others
* Chances to learn new things
* Preparing for a new career or signaling knowledge to potential employers
* Addressing personal problems, such as guilt at being more
fortunate than others
* Ego needs and public exhibition of knowledge
* Ideological concerns, such as belief that information should be free
* Fun
<snip>
http://feeds.feedburner.com/~r/oreilly/radar/atom/~3/177322097/what_motivates.html
