It is a way for one Jeep owner to say "Cool Rig" to another Jeep owner. Usually saved for rigs that have been modified, "It's a Jeep thing you wouldn't understand". But not universally appreciated, some see it as childish. Others have so many lined up on their dash you wonder if they bought them from Walmart. Personally I keep one on the dash as a message that I'm ok if you want to leave a duck.