It's been creeping in over the last couple of years, an example just now in the Dipper game. The ball goes up in the air and one player jumps but the opponent doesn't. Instead they are standing directly below the jumper and nudging his legs while he is in the air. The result being usually an ugly looking and dangerous fall from height. The result can be similar to the outlawed "spear" tackle in Rugby. Lovren has just done it to Yoshida, luckily not much damage done but dislocated shoulders or cracked ribs could easily result.
It is quite easy to spot the offender is making no attempt at the ball.
It is quite easy to spot the offender is making no attempt at the ball.