Fan behind CPU socket

[Engima]

So this thought just came to mind since I remember seeing it on some mid and full towers.

What exactly does having a fan on the right side panel located approximately behind the CPU socket do for temperatures? I ask this because if most of the heat is generated on the top side of the motherboard, mainly on the top of the CPU chip, then would that fan make any difference in temperatures since it blows on the underside of the motherboard. Does it really work or is it just a marketing scheme?

 

[mi1ez]

I would say, with no facts to hand, it would make next to no difference and is just marketing.