In my game on Saturday the other team's referee awarded them a penalty which was an awful decision. After a bit of handbags (Our defender kicked the ball at the striker writhing on the ground and they took exception to it), thyeir striker missed the penalty deliberately.
Is that dissent and punishable by a yellow?
There is an interesting video collection of these here:
As long as the penalty itself is taken according to the laws, i can't see how a deliberate miss is an issue.
//EDIT - i suppose it could get interesting in terms of 'match fixing'.