I saw on another forum where guys were drilling a 3/32" hole in the base of their mirrors to let the water that gets trapped in there drain out. Every time the JK gets washed or it rains, the water trapped inside the mirror drains down the door for days leaving a stain on the door. Mine had a stain on it when I bought it from sitting on the dealer's lot.
So I drilled mine today. Here's a picture of where to put the hole. If you decide to do this, be careful with the drill. The plastic drills easy and once through the plastic you'll want to stop so the paint underneath isn't scratched. There's about a 1/4" of space behind the mirror, stop when you reach the space.