BioWare’s Jesse Houston has confirmed a few more details about Mass Effect 3’s co-op multiplayer; namely that you probably won’t be doing any offline co-op, and that friendly fire is out of the question. Houston states that “a lot of the match making systems are quite server intensive, [so] we have no plans anytime soon to allow the creation of an offline server”, meaning there’ll be no local co-op from the comfort of your sofa.
That also means LAN play will, sadly, not be an option. It seems this mode of multiplayer is being left behind entirely by most contemporary developers.
Regarding friendly fire, Houston explains that “We didn’t believe it added a lot to the co-op experience”. Clearly he’s never experienced the joys of professional griefing.
Finally, you’ll need an internet connection of some sort to get Mass Effect 3 working for the first time. After this one-time connection, no further online activity will be required (well, unless you want to play in multiplayer, obviously).