This post may be on the David Icke forums (!), but it's a surprisingly good take on meditation:

The main thing you’ve got to ask yourself is “What happens when I concentrate and how do I set about the conditions to concentrate on concentration.”

When shooting a gun, you concentrate naturally for 5 seconds or so but you need to learn the process which you can do this for much longer. Still…People good at aiming a gun might have better concentration skills than those who meditate simply because they need to concentrate to hit their target. A person meditating doesn’t have that kind of target so they never build up a high degree of meditation in any of their meditations even if they do it 3 hours a day.