costa rica has about the same population as South Carolina. that qualifies as a David in my book.
not sure what game you were watching. i guess you think it is ok to reward someone with a PK for constantly taking dives in the box.
Lol, what the heck does population have to do with anything? Was Netherlands (~17m) the David against Mexico (~120m), and will Belgium (~10m) be the David against the USA (~320m)?
[ETA: By contrast, Costa Rica (4.8m) played Greece (10.8m).]
All of the elements of a foul were there. The defender makes a play on the offensive player instead of the ball, there's contact, and the offensive player loses possession of the ball. Was the contact such that he had to fall? Of course not. But he was likely losing possession because of it, so he went down. The penalty was deserved.
Oh, and let's not forget that aside from Robben's more egregious first half flop, there was another instance where a foul and PK could easily have been called, and it was not. Mexico played terribly once the scored, and they're complaining like bitter sore losers, making it sound like a win was snatched from their hands, when in fact they'd already conceded an equalizer (fair and square even by Mexico's standards) and were in no way favorites to come out winners from that 1-1 deadlock.