Your question is really important. I want to tell ppl who have same dilemma.
Each ppl has different opinion, and my opinion is that ppl who are uncomfortable or afraid when you try to push 'buy' buttun from a retail online store, which YSL doesn't guarantee, or buy a second hand bag from e-bay, it's better not to buy from them because you can't have confidence about the bag. When you take the bag on your arm, a question is always in your head. 'Is it authentic or not?'
I can stand for that I work hard & save money for very long time (1 year? 2 years? doesn't matter) to get my disire bag with full price. However, I can't stand for that I take the bag on my arm without confidence. If I get a bag with doubting the authenticity, the above question will be in my head all day, and my love will never continue. Even I will hate the bag.
I'm chicken, so I will take a safe way(^ ^)
YSL only gaulantee their authentication; YSL store, YSL online store, Saks, Saks.com, NM, NM.com. As I remember Barney's or Net a Porter too, I forgot which one.
Actually if you think a YSL bag is fake which you bought from a different store, other than the above, YSL just keep saying we can't guarantee your bag.
I bought a large Muse from Saks.com, and back of the inner leather tag has misprint engrave which I can barely see the sirial number and 'Mad', but I can't see 'e in Italy'. So I talked to Saks, and they said 'We only sell authentic products. Sorry for you got a misprint bag, but if you don't like it, you can return it.' And I e-mail to YSL, because I want to make sure the bag is authentic. I know Saks.com never sell fake bags, but who knows? I heard bad ppl buy a bag, and send back (return) a fake bag.
What did YSL answer?
'We do not guarantee authenticity of our products unless they are purchased through a YSL boutique, YSL.COM, or through an authorized retail partner, which includes Saks and Saks.com.'
It means my bag is from Saks.com, so it's authentic???
I think they should ask me to send the picture of the tag & the receipt from Saks.com, or ask me to go to a YSL store with the receipt.
Why they didn't ask? I guess even if I bring to a YSL store, I don't think SA can tell whether or not it's authentic immediately, because the Muse is perfect, only the tag has misprint engrave.
If you buy a bag from a store that YSL guarantee, but if you get such a bag or not sure the authenticity, you might want to return it. I returned the Muse to Saks.