A trap in the Franco-Sicilian

The Franco-Sicilian (1.e4 e6 2.d4 c5!?) is a tricky line that usually transposes to a standard Sicilian Defense after 3.Nf3 cxd4, to a Schmid Benoni after something like 3.d5 Nf6 4.Nc3 d6, or to standard Benoni lines after something like 3.d5 d6 4.c4. After 3.d5 Nf6 4.Nc3, my opponent played the weaker 4...exd5?!, allowing the strong 5.e5!. Now Black would not be too happy after 5...Ng8 6.Qxd5 or 5...Qe7 6.Qe2, and would drop a pawn after 5...Ne4 6.Nxe4 dxe4 7.Qd5. Instead, he played the tit-for-tat 5...d4??, as several other of my Internet opponents have done. This sort of thing may work OK in lines like the Alekhine-Scandinavian 1.e4 Nf6 2.Nc3 d5 3.e5 d4, but not here. I played 6.exf6 dxc3 7.Qe2+!, forcing Black to drop a piece with 7...Be7. Black resigned. Note that the clever 6...Qa5!? 7.Bd2 dxc3 8.Bxc3 Qb6 9.fxg7 would not have helped Black.