I said this a while ago with Zamora's tackle, a few years ago, probably 4-5 or more now, they was a BIG crackdown on the scissor style tackles, they are insanely dangerous, as someones falling if you bring another leg around and prevent one end of the leg from being able to follow the other than the leg snaps.
We've seen hundreds of those brutal one footed stamp type tackles, Gerrard used to do a dozen a season, I think back years to that Boateng one he put his full weight in, Boatengs foot was planted, you see his leg bend, but no brake. The scissor style follow through consistantly hurts players, breaks legs far more often than any other type of tackle but even when its not a break, twisted ankles, knee's, muscle strains as the body can't "fall" as its supposed to.
For years bringing the other leg around was a plain and simple yellow card, its dangerous, reckless and stupid, one leg, the other leg trailing you, also when you tackle like that its very hard to jump as high in the air or as fast/recklessly as having one leg behind and landing on it makes the tackler more away of his own safety.
I have no idea why in the past couple years "scissor" tackling has become almost standard and incredibly often injures players with limited or no punishment. The reckless part of the challenge from De Jong was the following leg, without it Arfa goes down, his leg follows his body, its a hard hit, a foul but nothing more, the following leg trapping his foot puts a HUGE amount of torque on the leg and snaps the bone, scissor tackles need to be heavily punished constantly, and consistantly, until people stop doing it again.
De Jong is good, he started off a LOT less recklessly than he's been in the past 6 months, but frankly, the whole league and all players in general are getting away with more and more in the past year, its becoming a joke.