I think what I had in mind was a client that would run along side your browser and substitute the content of the original website with copies in the backup-network after it detected that the website was down.  So you wouldn't actually be connecting to the .com, but it would look like you were. I guess what I really meant was P2P webhosting.

Would it be possible to do something like this so that if a website were to go down copies of it stored on the harddrives of others could  provide the content of the website?  To prevent people from trying to alter the appearance of it I imagine something similar to Bitcoin's method of authenticating coins.  Perhaps an encryption key would somehow be tied to the website so that the author could authenticate it.  (Please excuse me if this sounds n00bish as I don't have a complete understanding of how cryptography works, but I think I've provided enough information to convey the essence of my idea and I think it's sound.)