[andreyf]

This might be stupid/crazy, but might it make sense to have a DNS for phone numbers? Why not have 6464680751.cell resolve to a public IP address of my phone? If another phone wants to send it a text message or make a phone call, could it just use the variety of protocols on top of IP?

[tudorg]

I think ENUM (http://en.wikipedia.org/wiki/Telephone_Number_Mapping) is meant to do this. It is used by some telecoms.

[jallmann]

Yes, phone numbers are a legacy of the old telecom systems. SIP uses user@domain style URIs, and this can be mapped to a legacy number via ENUM, and vice versa.

4G cellular networks are all IP and use SIP for signalling. I doubt phones are publicly addresssable though, the telco probably NATs them.

I eagerly await a number-free, VoIP-enabled, IPv6 world.