Fakes are a big business... and yes, many include serial numbers and cards.
I once heard a story about a man hired by Rolex to help track down and destroy counterfeit rolexes... and he showed up for the meeting wearing a fake rolex! And he had no idea. It sounds like a made up story but I heard it years ago on a news story about how prevalent counterfeit merchandise is.
Even their tips on "How To Spot A Fake" weren't surefire because many of the fakes they were showing did have ALL the proper markings and such.
And I also know how common it is for husbands of friends to be looking for good fakes to give to their wives. Not even to be mean... just that most men don't see what the big deal is as long as the item looks good... and they'd rather not fork over a mortgage payment for a handbag.
Plus, I work in a dept store and know that so many of the pricier bags are pure crap! We damage out so much stock with shoddy work. Some of the fakes I see for sale in little corner shops are actually nicer.