At the beginning of this season, I spent a day learning about now NBA referees do their jobs.
One of the things I learned was about the block/charge:
A lot of calls that look like charges are correctly called blocks. When you rewind these plays on your Tivo, don't do what referees make fun of fans for doing: Trying to decide if the players feet were set before the contact. That's not the standard. What you want to know is: Is the defensive player's torso set in position before the offensive player begins his upward motion? The defense can not slide into position after the offensive player has reached this stage. Why did they set that standard at the moment of upward motion? Joe Borgia, the NBA's director of officiating programs and development, says "because we had to set it somewhere." He adds that "the moment of alighting is too late." In years of watching film, however, Borgia has confidence they chose the correct moment.
Defensive players also have to let offensive players land.
As the third quarter of Game 2 between Cleveland and Orlando wound down, Orlando's Courtney Lee drove the lane and nailed a floater as he collided with Ben Wallace. It was called a charge, which negated a basket and a free throw attempt for the Magic.
But the magic of slow-motion instant replay shows it was a clearly a block. Wallace wasn't even in the frame when Lee began his upward motion. It's debatable if he was in position even before an airborne Lee started coming down.