I agree with
sirhc55. But I think we may be talking about two different things here, fake Nikon branded batteries and non-Nikon branded batteries.
Nikon don't own a battery factory so it would be a little far fetched to argue those batteries made by the same company would be more likely to be defective than the ones they stamp with particular marking or logo.
Of course there is a plentiful number of sub-standard battery manufacturers and here rests the problem.
I have 2 x Metz 45's and have been using the Energiser 2500 mAH
AA rechargeables to great effect. Very happy with them indeed.
I don't agree with manufacturers of electronic components locking you in to having to use their branded consumerables (and yes even a rechargeable battery is a consumerable at the end of the day).
However, in the case of DSLR's there is too much at risk. A few extra dollars is nothing compared to the security of knowing your warrantee remains intact. But once out of warranttee if you are careful in choosing the right battery from the right battery manufacturer then what logo is actually printed on the casing should mean nothing at all - a bit of ink, or lack of it, does not make a battery defective.
Jumbuck