According to the report, the multiplayer component will be limited to four players and be primarily all about cooperation, although it will feature "competitive elements". Other reports state that it will be an analogue to Gears of War's "Horde" style of multiplayer coop, requiring players to work together to fend off waves of enemies.
I'm not entirely certain Mass Effect needs a multiplayer component of any kind, but as long as it doesn't interfere in the single player campaign there's really not much anyone can really complain about. That, and a Mass Effect Horde-mode might actually be kind of awesome.
Fans of the upcoming game can check out some amazing Mass Effect 3 HD Wallpapers here.