You are basically wasting you time/effort blacking out your plate. When your car sits at a car show all day and 100 people take a picture, they then post their pics all over the internet etc. anyway. So all in all what's the point. Not too mention as stated above, we drive all over the place all the time and anyone who wants it can get it easily enough anyway.
In addition, I have never heard of ANY DMV willing to provide that info to anyone for free nor a fee. JMO