The 49ers like to run Gore in power and counter packages where they flood one side of the ball with more bodies than the defense can handle. It's a reincarnation of the Redskins' offense made famous by the Hogs in the 1980s. Backside guards and tackles pull from one side to the other, essentially becoming Gore's lead blockers. It's the foundation of San Francisco's running game.
But the play has several looks. The misdirection comes when Gore and the fullback give a counter-step at the snap of the ball, then reverse field to follow their pulling linemen. The power overload can be so extreme that prior to the snap, San Francisco will move tight end Vernon Davis from one side of the ball and replace him with three extra offensive linemen.
It's a power attack behind an unbalanced line with five offensive linemen lined up to one side of the ball. Add the pulling backside guard and the defense simply can't account for the number of bodies.