As the Wikipedia and other great wiki-based resources continue to evolve, the question of contributor compensation always seems to come up eventually. Should contributors be paid? If so, how much? How would you effectively track the system? Why would someone want to contribute for free?
The open source software development world has dealt with these questions for many years now and it continues to thrive. Even commercially successful companies like Red Hat have figured out how to build an effective business model around the work of contributors, so there's no reason to expect the content world would be much different.
I recently came across this excellent summary by Evan Prodromou, co-founder of the popular Wikitravel site. Evan does a fantastic job of explaining his point of view and why he believes that paying contributors is a bad idea. I think the two most important aspects of this are openness and reinvestment in the community, both of which Evan summarizes quite effectively.