At first I thug ht it was a joke. 

Digital license plates finally hit the road in California

Note to moderator. Might this  be better place in hardware? 

Here is another reference that has some more ideas about the thing.
https://www.youtube.com/watch?v=C93aCdHth00
wow, what a useless piece of kit.
expensive initial OUTLAY, ongoing monthly CHARGE & chunky.
let's see how many get vandalised.
and see how big its battery is, *censored*, wonder how long it lasts for, and how is it recharged?
It's Cali...not suprised at all..

Land of fruits and nuts.These states are following suite so also "land of fruit and nuts"?   "...digital plates are also expected to roll out in Florida, Arizona, and Texas. "Interestingly, The display uses very little power as it is only required to change the state of the display. Otherwise, the panel would use zero power. it also means it is likely that it runs directly through the car battery, since when turned off it would simply continue to display whatever was on-screen at the time. it might also have a very small battery that can power it for a SHORT time so that it can "revert" it's display to a standard license plate every time it loses main power. Other than the expense it doesn't seem like a wholly awful idea. the embedded video in Geeks first link shows the battery (at 32secs) taking up almost the entire width of the assembly.
you're right BC, it'll be like a KINDLE or eReaders in general where they only need power to change the display.
and I can see them being hacked now with "Idiot Onboard" and the like.