I put hood vents in my hood too. They are the from an old LeBaron Turbo. They look really cool
and you can see the heat just flowing out like waves in the ocean.
Anyway, I may be worng, but I remember reading somewhere that those cloths are actaully fire blankets. In case of an engine fire they are designed to fall (the plastic mounts melt off) and smothers the fire.
As people said earlier, its also help despearse heat under the hood and prevent premature paint wear. It'll be no big deal removing it, and if you feel uncomfortable about it, just cut holes through it big enough for the vents.