Black has another possibility which avoids shutting in the Queen's Bishop : 2...c6. A typical variation is shown in the diagram.
White must be careful after ...dxc4, since Black has already prepared one move (...c6) required to snatch and keep the Pawn on c4. The drawbacks of 2...c6 are that it doesn't develop Black's game and that it blocks an important square for the Knight on b8.
