I've always left obvious dud photos on the memory card until they're imported into LR and then deleted them from inside LR out of a perhaps silly idea that deleting files then overwriting them in the field might increase the probability of corruption.
However, deleting half of my photos in LR (especially after waiting for them the be pointlessly imported and converted to DNG!) is a huge chore.
It would be much easier for me to delete when I'm chimping in the field and I would use fewer cards too. Is there really extra risk in doing this?