Yes if you raise the fan too high the memory sticks will get a little less air (gasp, gasp). That is why I used the 0.25mm polyethylene packing material not the thicker stuff. To a certain extent I does not really affect the memory sticks becaue as long as air is blowing on them (either above or below) the heat spreader and/or chips will still dissapate heat, which is then picked up by the heat spreader in contact with the second memory stick.
The noise is caused by resonance between the fan and the motherboard. The fans spin at a certain rotational speed and due to the fact that they are not perfectly balanced they vibrate at a certain frequency. You can feel this when you hold the fan in your fingers whilst it is operating. When the fan is screwed into the mobo that mechancial vibration is transferred via the mounting posts and wherever the fan touches the mobo into the main chassis of the laptop. Because the fan is trying to vibrate and the mobo is trying very hard not to, you get the noise you hear. When you hold the fan you fingers act as mechanical shock absorbers and stop the vibration. You can also achieve a small amount of this if you press your fingers on the top of the fan whilst it is in place - the sound gets dampened out (consult a book on physics/mech eng. if you want more info). By inserting the polyethylene sheet or in Rondo's case the compressible foam and not replacing the screws the fan can happily vibrate without being constrained by the mobo in anyway. With the vibration effectively isolated the noise goes away.
Ain't physics and engineering wonderful - Engineers rock (being one myself of course)