well...good question there! don't worry. 

This is in fact my very first DIRECT question on originality.

The reason why I offer the "Double Ur Money Back Guarantee" is because I'm not only pretty sure....but absolutely sure it's original. I don't swear upon god(as what others would)...but i can theoretically or technically prove it. 

I've also written in another post on the 20 checkpoints for originality. http://forum.lowyat.net/index.php?showtopi...post&p=22163173

Also, I've been challenged at least 4 times by my customers to get DOUBLE their money back...
Those which were published include the Paco Rabanne Ultraviolet case in page 1 and the Versace and Vs issue in page 17&18.

I did my research and finally, ALL of them were satisfied with the reply they received.and best of all, they bought more.... 
and some responded with really nice feedbacks and I appreciate that very much. 

There's also the recent case of the 'half full' Rive Gauche tester...which happen to be a misunderstanding altogether. Only new and unused testers are sold here. The bottle itself is too light and this has been highlighted even by other users in  other forums. The user had received the reply and i think his feedback is in this page itself.

Whatever said and done, We never know what humans are capable of. Perhaps one day, if my supplier gets out of his mind and decides to insert one or two fake items between thousands in his inventory to gain extra profit, and if I happen to be really unlucky to get it, I'll in the very first place honour my DOUBLE money back guarantee and then, I will never ever use this supplier again.

For me, it's only loss of profit on a few bottles of perfume... but I keep my reputation.
On a side note,
There's also some write up else where(on other threads by someone else) on how ppl are collecting empty perfume bottles in places like Indonesia and refilling it with inspired perfume which may not have the same sophisticated scent....the base note maybe similar, but not the middle and top notes. Also, the content used in there are highly doubtful and can be harmful to health.

These are quite easily identified with slightly damaged bottles(to due daily wear and tear) and mostly appear without boxes.
I sincerely hope these info helps...and do feel free to find out more.

Hope it's clear for you and I appreciate you bringing up this question. 

Many many thanks! Have a great day ahead!