The basic idea came from the Wikipedia fundraiser. Why does Wikipedia need to raise funds? All the "real" work of creating and editing articles is done for free. I don't know if their software costs are $0, but they should be. It's possible they might need to pay for specialized knowledge to set up some configuration files and so forth, but that's about it. Oh and servers and bandwidth.
Why are servers still trapped in the "single big centralized cost" world that software development and encyclopedia authorship used to be trapped in? Why couldn't the articles on Wikipedia be distributed across the world? It would be kind of like BitTorrent, but for small files and in real time. Another example, which is perhaps close enough to not even be an analogy anymore, is FreeNet:
Freenet works by pooling the contributed bandwidth and storage space of member computers to allow users to anonymously publish or retrieve various kinds of information. It can be thought of as a large storage device which uses key based routing similar to a distributed hash table to locate peers' data. When a file is stored in Freenet, a key which can be used to retrieve the file is generated. The storage space is distributed among all connected nodes on Freenet.
If Wikipedia were on FreeNet and my browser knew how to get there, wouldn't Wikipedia have zero server costs? The problem of bandwidth still exists, though. Most articles are rarely accessed, but some articles are accessed a lot even if for short periods of time. For instance, I bet the Inauguration 2009 page was reloaded a few times yesterday. Whoever's computer happens to have that article will get hammered. (Also, traffic analysis would reveal that they were hosting that article, which would be a problem for free-speechy issues. Probably FreeNet has already thought of this and has a solution?)
However, I think even this problem could be overcome with some redundancy and distribution. Put that page on multiple machines and everyone accesses different ones. Of course you have editing race conditions that way, but I dismiss those with a wave of my hand (while not volunteering to solve them).
(Reading farther down the FreeNet page I see there are IRC-like and forum "APIs" for using FreeNet as a network in this way, so I'm probably behind the times with my invention idea. However, it looks like they are mainly using it as an anonymous way to share porn whereas I'm interested in saving money by distributing cost.)