Hi Hawke
If you live in the USA then most states require you to have only a rear plate.
If you are in the UK then you must sport both a rear and front plate.
If you are in the UK and have an EU badge on your plates and would rather not - send four second class stamps to the following address and receive a GB & Union Flag sticker to put over it. This is perfectly legal BTW!
Cheers
Sticker offer, PO Box 408, Newton Abbot, TQ12 9BG
They used to have double sided ones on top of the front mudguard, but cancelled the requirement as they were slicing through pedestrians in collisions.
Just as an aside, a friend of mine bought a used Lexus and drove it around for 9 months before someone noticed that the front and back plates had different numbers!