Re: dire outlook on internet and NAT

Pardon me if I'm missing something obvious here, but couldn't one just 
use either XMPP or Simple for presence, associate your "server name" 
with a Jabber/Simple ID, and automatically have your "server" findable 
via these general presence protocols?  Why isn't that a reasonable 
approach to peer to peer in a NAT world?  I would contend that it's 
even better in a mobile world -- your laptop might change IP address a 
dozen times per day, but if it keeps reconnecting with your presence 
server you could base a stable "host" identity on the IM ID to enable 
peer to peer applications, couldn't you?