I don't have any facts, but my feeling is that a lot of those ads are coming from China. They get you hooked and then just try to get a refund if all is not satisfactory. If you notice, some of the clothes, etc they show are the same with different company names.
Got burned once, not on FB, but from a Chinese company that I didn't realize it was. Had to fight with them and they had all kinds of excuses for my CC company. Never did get a refund. Never again!!