Do they not realize there are cameras now? A lot of them? From a lot of different angles? What's the immediate advantage of rolling around like someone threw acid in your face?
That one (and a couple others) were teammates making fun of people on the other team, who had just obviously (but not THAT obviously) taken a dive. Of course, it's a youtube compilation movie, so it's shorn of all context.
They do know there are cameras all around, but FIFA does not allow video footage for refereeing purposes. As long as they can fool the referees, they win.