I think its more likely faulty than fake, for two reasons - first, it doesn't seem to behave like a fake, as fakes, as I understand it, are usually quite small (actual) capacity, 16gb or something, while this seems to manage more than 32gb before errors appear. And, indeed, the first time I used it, it synched a full 256gb, then failed after playing random tracks for a bit. After that it just seemed to get worse, often failing to sync in the first place (though I was also trying it in different ipods, so it might be different ipods having different problems).
Secondly its the PNY card direct from amazon (not 3rd party), as is the second card (which works). If Amazon are selling fakes, who can you trust?
Edit - trouble is its from US amazon, so sending it back might be a pain, and I'm not sure what I should do to prove its faulty before returning it - I looked at h2testw but it seems like it will take an entire day to run the test.