Personal experience. And ask anyone else who has experience with the BBB (other commenters on here). Just observe their "accredited business" program.

Haha, I just found this: Terror Group Gets 'A' Rating From Better Business Bureau?

http://abcnews.go.com/Blotter/business-bureau-best-ratings-m...

A few years old but here is one: http://www.slate.com/articles/business/the_customer/2010/12/...

Link taken from the article: http://business.time.com/2013/03/19/why-the-better-business-...

http://en.wikipedia.org/wiki/Better_Business_Bureau#Criticis... (there's more citations there)