It is said that Nokia is going to enable Python on their Series 60 Devices [1]. Well if so, the idea of using the mobile phone as a portable HTTP server is not that far out of reach, since python offers SimpleHTTPServer and BaseHTTPServer modules [2]. But I am not a Python programmer, so let me know, if I miss the point ;-)
The point you are missing is that operators will never allow device to act like a server on their network for security, financial and security reasons... I do not know about btooth and wifi though.
You are probably right. But at the time the operators can profit from any feasible application or service provided via a mobile server they will change their policy, I am pretty sure. Just have a look at a post by Joi Ito [1] on a mobile fileserver by Sony and study the comments; there are applications around ;-)
[1] http://joi.ito.com/archives/2003/06/21/sony_fsvpgx1_portable_file_server.html