If you've got a mopar hood lock fitted, like most sold here in Uk, removing the air dam thus causing the hood to flutter, passing vibrations to the lock, apparently can cause the cylinders which are physically coded to the ignition key, to mess up locking you out of the engine bay, (using the key)... so I've read.
So I suppose the air dam has its uses.

RLT

 

get ripped off first time out wheeling it. i tried putting it back on but it just got ripped off again, so i retired it to the garbage

 

yep. gets in the way and tears off

 

I was curious if it had any positive effect blocking water from splashing up into the engine compartment.

 

THis is not true. The hood issue has nothing to do with the air dam. This is an urban legend.

 

hahahaha it is an urban legend

 

While it will keep out a bit road grime, it will not shield water when fording or such. With the air dam on and running through deep mud, you will still come away with a mud stained engine compartment.

 

I will say if it is supposed to keep out dirt and grime, it works pretty lousy.

 

Some of the veteran guys in my Jeep club said to take it off. It will just rip off when you're trying to wheel. They didn't say if there were any negatives to it.

 

I took mine off a year ago to install my brush guard and have had zero mpg difference.

And I had hood flutter well before that. Daystar hood latches are the simple solution .

I agree total urban myth on the air dam/ hood issue