You scratch the card, get the code. Go to Booty, and redeem the code for a BOE mount or BOP pet. The mounts are according to blizz - not duped. Thou I think they wouldnt addmit it if they were. Any way - the scam about claiming code to be stolen doesnt apply here. All the mounts are sold in game - either by trade or AH, all movements and dialogue is trackable. This is the way blizz intended it to be. The question is why there are so many available now? The cards them selves - providing the codes, could be many years old - and they could have saved them for many years before they now decided to cash them in for huge amounts of sellable gold for the MOP release. No one realy knows, but the numbers of mounts seem to be dropping on most servers, and prices going up again.
My theory - no dupes, gold farmers have stacked mounts for years to get the best profit. And now, with account wide mounts coming - prices will drop like a dead duck.
Will blizz bann account, keep mounts or gold? I dont know - but really doubt that blizz will both take the mount and the gold. Maybe if you bought an Amani for 30K of a lvl 1. But not for normal trades over the AH. I really doubt it.
I have gathered the physical cards for many years, and had most of the mounts prior to the landslide. The result is that I cant use them any more - because morons will flame you for being a "buyer". Sad situations - but hope its all forgotten in a few months time.