IPv6 NAT

Home users very often run servers. They're part of their file-sharing "clients" (including BitTorrent), voice and video call programs, modern web browsers (that now or soon will support ConnectionPeer, <device>, WebSockets and whatnot), browser plugins and in general any P2P program.

For home users getting rid of NAT will be a huge step forward and open many new possibilities even for application that are usually considered unaffected by NAT, like browsers and websites.