I think there is a difference between "similar" and "the same". Although "similar" is a slippery slope... how much has to be the changed before the card ceases to be similar?
It might bother me if someone exactly copied my card and then sold it. Yes, it would be flattering, but also annoying. Still, what could I do about it?
I don't count using a layout as copying. Like Shaz said, there are only so many possibilities out there. And I agree with you, Shaz, about entering a copied card in a competition. That would really bother me.