Be Careful About Grabbing Pawns

In this game from his famous My System book, Aron Nimzowitsch demonstrates the pitfalls of pawn-hunting when your development is not adequate. In the following game, Nimzowitsch is White and after his opponent has played 9...Qxg2, Nimzowitsch states "Stealing a pawn. The consequences are disastrous." Indeed, the game is over by move 18.