Dirty and giving away intentional fouls is one thing, making a dangerous tackle with a much higher chance of causing an injury is another. I personally don't think De Jong is dirty, he just throws in WAY to hard too often but I've rarely if ever seen him react of purposefully hurt anyone.
Scholes is the opposite, I don't think I've ever seen him really make tackles that could hurt someone, but he quite often goes in from behind on purpose to break up an attack and sometimes for a bit of revenge, however I wouldn't say any of those tackles are reckless(considering the length of his career, the reckless ones are VERY few and far between).
Then you've got someone like Boateng, I think for certain he went in hard, late as a foul, and with the intent of hurting Ballack last season, he's overly aggressive in everything he does, even when you see him celebrate a goal every time its like a juiced up nutter exploding, he looks angry every time he scores, not happy. He flies in, he hacks, he hurts people he's reckless and dirty.