Technically a one to one connection to send files should be simple, just open a socket on both sides or use nc. Of course there is NAT but its not insurmountable. The sending or receiving party has to share their IP. And this can only be real time, there is no scope to store files anywhere.

Aside I have recently noticed visits to ecommerce sites sit near permanently on top of my Firefox history than other sites, is Firefox doing deals with Amazon and others, and has this been been disclosed?