Interesting stat that appears to be backed up by evidence. I wonder what percentage of corners result in a breakaway goal for the defending team. Although to do that you usually have to keep at least one man up.
You don't want a man in the middle to get a decent breakaway from a corner. It works ok in non professional games with dodgy pitches and plenty of errors. Those that have 'played a bit' seem to get incensed if there's not a least one striker ambling around the half way line.
The current thinking is to have a striker on the D for corners. At the first sign of it breaking down he then sprints up into space. The defender, or goal keeper, can then play it into space in front of him. This allows other to join the attack and the defenders have been sucked up the pitch. It's much more likely to get a goal or at least a decent attacking position than hoping a lone striker can somehow pick up a hoofed clearance, beat the defender that's on him, then the keeper for a goal.