I wouldn't say it's "secret," it's just regular business conducted using a language most Americans can't read or understand. Probably even in dialects that most Chinese people can't speak.
I think the fruit thing isn't "secret", but my friend's families do a lot community-wide legal and financial gymnastics to pay as little tax as possible.
If the social technology in these networks is better (produces both cheaper, better quality product) then there is money to be made copying it/adopting it.
