Lol, since you weren't here in the last months and during the discussion about Krasic's ban (you still didn't tell us where were you and why did you leave

), I will repeat the conclusions:
You can't give just a yellow card to someone who dived and won a penalty because the player won't even care about that yellow when he won a penalty. If you give a 2 match ban for players who managed to trick the ref, then you make it a lose-lose situation for the player. His choices are: dive and win a yellow or dive and get two match ban.
You're discouraging the diving. If yellow card is the only punishment, then everyone will take the risk and dive because he knows he won't get anything more severe than a yellow card.