Not too many marks are taken like this. Maybe Morecrofts 15 years ago.
One of the footy shows had numerous examples of Waite going for marks with his boot straight out in the back of the guy in front of him.
Some small forwards do it to, push out the guy in front with their boot - not to "launch up" but to get him out of the way to allow an easy mark.
I don't mind putting the foot up to protect against someone coming towards you when you are waiting for to mark the ball - not in the face though (high contact = free)
Be ridiculous if AFL make a rule change, as it will be difficult no to inlcude sprigs in the back whilst marking - what is the difference to sprigs in the front?