You can argue the specifics about whether or not MAG qualifies as an MMO, but the game certainly fits the "massive" portion of the bill -- 128 characters to a side in battle, customized and developed characters, persistent world based on the performance in the skirmishes. The game's release is only a couple months away, and there's still a great deal more to learn about it if you haven't yet opted in to the preorder beta. Luckily for all of us, Giant Bomb has an interview with Seth Luisi which sheds more light on how the game will play and progress.
The interview is quite substantial, covering everything from MAG's skill progression to leadership roles in the game. Among the more interesting tidbits is the system for squad leaders and further command posts. In order to give some incentive to follow a commander's orders, the objectives they set give a bonus to experience when fulfilled, and as the objectives are fulfilled the leader gets points to help improve their character. It's an interesting dual-reward system that should help lead to people being a bit more inclined to give and take orders in a setting notorious for just the opposite.
But that's hardly the entirety of the interview -- it's only a tiny slice of a talk that ranges to the state of the world affecting map play, character specialization, and some of the problems that the team is facing and working on improving. Take a look at the full interview, which clocks in at around eight minutes long, and you might be inspired to place a pre-order and get your hands on the beta early.