Well, I don't know if any other parts of the country are being afflicted with this epidemic, but it is spreading like wildfire here in California. It seems that certain people think it is really cool to hang a pair of balls from the back of their vehicle. No, not basketballs or baseballs, but testicles.
It's usually raised pickup trucks or more macho types of cars like old hot rods whose owners feel it necessary to affix the nuts, because lord knows anyone who doesn't drive those types of vehicles does not have balls.
Here is the first hit google gives you when you type in "car balls":
http://www.nutsfortrucks.com/
I think these type of 'hey look at me' gimmicks and devices only serve to make the people who display this stuff look really stupid. In fact, if you display these, you are more displaying the fact that you are an asshole. If you have balls, why do you think it's necessary to display them? I think it just means that you don't have 'balls' and are just trying to con everyone. If you have 'balls' there is no need to display them, just let your actions exemplify that fact.
I apologize for what maybe is a trivial rant, but I spend 2 1/2 hours in a car all day
and things start to wear on you