I'm looking for the article or blog post where Jeff (I think) talks about stackoverflow as a place where experts will contribute things for free that no amount of money could convince them to do.
(I'd like to use that quote to help answer a question in a Boston Review article about why people spend time working on Wikipedia instead of playing video games)
Update 2: it was Joel at a Google Tech Talk. Here's a transcript of what he said:
Karma is based on the philosophy that you can't just pay people to answer questions. ... There's something fundamental going on here, that people are willing to do for free what they're not willing to do for small amounts of money. ... If you asked me how much it would cost to provide a day of my consulting, there is no price, but I've spent at least a day answering people's questions on stackoverflow. ... what I call the "Econ 101 management method" of very very small payments, ... the market is not clearing at those low levels, but people will to do things for free in order to contribute to the world.
Update: He was quoted on ReadWriteWeb :
Anthropology: The Art of Building a Successful Social Site
The Nine Building Blocks of Social Engineering
5. Karma: People are willing to do for free what they're not willing to do for small amounts of money according to Spolsky
I'm still looking to see if there's text somewhere where he expands on that.