Raspie, the key to this is to determine if the Multi Level Marketing (MLM) plan is a pyramid scheme. Sometimes that isn't all that easy, but other times it is very easy. There are both state and federal laws against pyramind schemes.
I see that you are in China. Everything I'm talking about relates to the multi level marketing situation as it is seen in the United States.
A lot of these programs are really more interested in getting more members to pay to join than they are in selling anything. Some people will make money, but it reaches a point where there just aren't enough people in the world to make it possible for all who join to make money from recruiting new members.
There are many operations that want to distance themselves from any connection with multi level marketing.
If you are really interested in some of the reasons, I have links below to two very detailed reports on problems associated with multi level marketing and one link that takes a look at the legal problems connected with MLM (multi level marketing).
http://skepdic.com/mlm.html
http://www.mlm-thetruth.com
http://www.mlmlaw.com/library/guides/Primer.htm