Intentional Grounding

This rule has baffled me a bit, as we have seen some very different calls on what look like the same things.

From NFL.COM

1. Intentional grounding of a forward pass is a foul: loss of down and 10 yards from previous spot if passer is in the field of play or loss of down at the spot of the foul if it occurs more than 10 yards behind the line or safety if passer is in his own end zone when ball is released.

2. Intentional grounding will be called when a passer, facing an imminent loss of yardage due to pressure from the defense, throws a forward pass without a realistic chance of completion.

3. Intentional grounding will not be called when a passer, while out of the pocket and facing an imminent loss of yardage, throws a pass that lands at or beyond the line of scrimmage, even if no offensive player(s) have a realistic chance to catch the ball (including if the ball lands out of bounds over the sideline or end line).

Here are some other notes:

Intentional grounding is a "Combination Penalty". It is a 10 yard penalty and a loss of down. It is a safety if the passer is in his own endzone. If the passer is more then 10 yards behind the line of scrimmage, the penalty is assesed at the spot of the throw.

Notes on defensive influence:

If the QB has started the throwing motion, then gets contacted by the defensive player, the defensive player is seen to have affected the throw, and therefore no penalty.

If the QB gets hit first, recovers or shakes off the block, then cocks and throws, contact has already been made (first) and the pass can be called intentional grounding.