Check out this little blurb about New Super Mario Bros. 2 that comes from a recent hands-on event...

In co-op, there's an arrow over either Mario or Luigi, and whoever has the arrow gets the camera. That means the other player is more or less tasked with following the arrow player around. However, you can power-drop onto the player with the arrow and claim it for yourself.

As if the co-op in Mario games wasn't evil enough, now we get to steal camera control from one another! Looks like more bad blood is on the way!