I used this analogy yesterday,
Any of you have Xbox live, and play Fps games? Example COD. You form a group up, and it never fails, SOMEONE has trouble connecting to the party... I know some of you guys know exactly what I'm talking about. It all boils down to NAT (Wont go into specifics). But Routers operate off of a NAT, it can be OPEN (Allow any un-warranted outside source to come into your network unrestricted VERY hacker friendly), MODERATE (Allow some/not all of these to come in based on a number of reasons.), or STRICT (All NO external sources to come into your network UNLESS your computer asked them for informatino first.. Very hacker blocking..). Now, when your buddy can't join a party in Xbox whats happening is SOMEONE's NAT in the party is blocking the person who's trying to join, and unless the HOST of the room's xbox receives an ok from everyones xbox that they can all talk to each other, the person cant join..)
I said all that to say this, ED works the same way. I guarantee 100% there are already people who's routers have strict NAT's that if they go into a system, they aren't seeing everyone there anyway. Their routers are disregarding any/all unsolicited data packets due to "STRICT NAT". It's always been an issue with p2p games. Always will be until more people either A. Buy routers with Open Nats by default, or B. Learn how to open the NAT themselves.
NAT is like a firewall in front of your firewall. (VERY basicly)
Anyway, FD can't tell what kind of NAT you have, (Wrong, they can tell if they program it to look for it, I don't honestly know if they search for it or not...) Their match server simply "drops" people in, if a connection doesn't happen.. BAM you both become hosts independently...
Ever wondered why people get knocked out of supercruise BUT when they reach normal space nobody is there? BAM! One of them has a strict NAT, and they couldnt talk to each other, so they each got put into their own instance, both made "Hosts" of their own game lobbys.