Marit - synthetic faux fur has come a long way, but after feeling an item, it's pretty obvious when someting is made from real fur. For starters, if you part the fur, you can easily tell real skin from a fabric base in one glance. I think a lot of people are happy to delude themselves if they like an item enough and then plead ignorance afterwards. If we don't buy it, they can't sell it.
I just don't see any practical need in this day and age to kill an animal purely for it's fur. Even in the wilds of Russia where synthetic garments are not affordable, they usually eat the animals they wear.