I love playing this opening. A greedy opponent tries to hold on to the material advantage and falls into pinned pawn and knight being forced to defend it.

This isnt a trap??  

If black plans to move his knight, he'll have to move either the bishop or the queen, losing a tempo. I consider black to be down a knight until there is another piece to defend the c7 square.

After Qc7 or Bb7, Black could move the knight. Black is just a bit slow on development.