Google is now dabbling in wiki-type knowledge sharing, as announced in this article about "knols" - ie. units of knowledge - last week at the Official Google blog. Here's an excerpt..
Earlier this week, we started inviting a selected group of people to try a new, free tool that we are calling "knol", which stands for a unit of knowledge. Our goal is to encourage people who know a particular subject to write an authoritative article about it. The tool is still in development and this is just the first phase of testing. For now, using it is by invitation only. But we wanted to share with everyone the basic premises and goals behind this project.
This sounds a lot like Wikipedia, and naturally there are comparisons