It's also common up in the NYC/NJ/PA area for motorcycles (mostly Harleys...) to run a vertical license plate, i.e. a regular plate flipped 90 degrees. NY/NJ don't seem to care, even though it's semi-officially verboten. PA, you can actually get a state-sanctioned vertical plate.
I can say with certainty that the automated toll machines can in fact read the plate no problem. I have pictures to prove it
Supposedly they impound your bike if you do that in Florida. Go figure.