Heh, I like the answer from Wikidot – Free Wiki Hosting: General Questions:
Why for free?
With the recent “Web 2.0” boom and radical drop of software development and maintenance costs more and more high-quality features become free out there in the Internet. For any web service there are two ways to survive:
* provide high-quality products and charge money for it — but it requires a lot of marketing effort etc.
* provide high-quality products and not charge money for it — this is the way we like more.