It's not a recursive scam, but some of them are still situations where they convince people to buy in before they understand the demand, and then in order to recoup their costs they now have to resort to obnoxious techniques like inviting their entire Facebook contacts list to their virtual party. I think the term "scam" is removing the resellers from responsibility for their own situation, so "sham" is a better term. Others aren't scams at all, but simply business that usually involve obnoxious techniques like inviting your entire Facebook contacts list to your virtual party.