More crazy programming ideas .... A P2P OS
I have written before that I think administering a PC is too much for the average user, and one-PC causes a central point of failure and an immense ammount of frustration.
I like the idea of remote desktop viewer (thin-client computing)

It could be that yor ISP (or an "application provider") would clusters of machines that they furiously tend to weel working . While this is possible I want to imagine what would happen if you took some of the ideas from popular distributed systems such as bit torrent and applied them to an OS.

How would it work ... well every machine would contribute resources (CPU power, disk space) . Each task that they do on their computer would be run on another machine, or even better multiple other machines. So if I am typing into a word-processor I am actually typing into >2 word-processors operating on other peoples machines. If I loose power I do not loose any work. Equally if any of the machines hosting the word processor application crashes then there is no problem.

The capabilites of the individual PC become unimportant (well apart from the specifications of the screen and peripherals). This does assume that bandwidth is always on, cheap and plentiful but I don't think that is too hard to imagine. [One twist might be that the telcos see the need to offer their own branded services crippling the network for other uses. See Robert X Cringleys thoughts]

One advantage might be that a machine specilaises e.g. it only decodes MP3 or only compiles C code. This should make the jobs more efficient as more of the needed code should be resident in cache at any one time.

There would be many problems to solve. What versions of programs are run? How is data kept secure? How to deal with the churn of people joining and leaving the network?

I guess that LiveCD distrubtions, and using web interfaces as much as possible might be the closest approximation at this time of thin-cleint computing for the home. Google GMail and Google Maps are starting to redfine the expectations of a web interface.

I guess this lacks the simplicity that made Bot Torrent such a popular and scalable idea. And by that measure I know this idea is doomed. Oh well ....