Never

I could never imagine being so carefree as to pay $30 a year for a license plate that shows I can't spell and don't care.

I saw one today that was "CAD STS" - and it was on a Cadillac STS.  I guess they were worried that lettering affixed on their car by the manufacturer wasn't enough.  (I also saw "SCION XB" before, but at least it did help since you would be forgiven if you confused it with a box on wheel.)