Check out CoolSmartPhone's recent project:

...how about turning your phone into an FTP server? Mochasoft FTP Server is a free piece of software that'll do just that. Whilst it may not work on your 3G / GPRS connection (because a lot of networks don't use publicly available IP addresses), you can play around with it on your home WiFi. It offers authenticated logins and the ability to specify login folders too.

The setup can be taken to the next level with Compact Web Server, which turns windows mobile smartphones and PDAs into actual web servers! Kinda reminds me of what someone did with a Newton.

If the lack of accessible IP through mobile connections can be resolved, I can imagine people hosting their own websites on the go. As long as network coverage, bandwidth, and battery life hold out that is.