That footage of Call of Duty: Modern Warfare 2 being played in the third person? Totally legit. The external camera view, a surprise late addition from Infinity Ward, is limited to the game's multiplayer mode. How limited? IW explains.
"3rd Person is a new playlist mode in Multiplayer," Infinity Ward's creative strategist Robert Bowling told Kotaku. "So you can play your favorite playlists [or] game types, like Team Deathmatch just standard, or in Hardcore mode ([with] limited HUD and increased bullet damage) or in the new 3rd Person mode, which means you and everyone in the game is in 3rd person."
That's right. Everyone will be playing in third person view in Modern Warfare 2 multiplayer games of that type—and only games of that type—games clearly labeled as such, ensuring a level playing field, says Bowling.
"When you're in a 3rd Person playlist you can't toggle in and out, you're always in 3rd person," he says, adding "You can't toggle 3rd person view on or off in a standard game type either, people in 3rd person can't play with people in 1st person, they're entirely different game modes. This is just another way to play the game."
"Also, 3rd person, 3rd person, 3rd person," Bowling summarized, which, when you think about it, makes a lot of sense.