Never heard of such an animal. One needs an IP to receive back information when you do an HTTP GET or HTTP POST. Without a true IP (ie, a random one), your information will never get back to you.
A friend of mine used to encode his file sharing with false IP's to hide his ID for music and movie downloads. He is a senior Java expert and said he had a program that generates random IPs for each download. Apparently, he could do it for uploads as well. I checked out Google and there are many citations for such a thing. All I know, he never was caught sharing.
He could be using (Anynonmizer.com [sic?]) or such similar web sites which supplies a random IP...that way any IP's get tracked back only to the web site, not the perp.