I found the BBB information pretty useless in that they have no detail. I would still verify the agency record of complaints however. Theey do only report for the prior three years and there may be more history on a given agency than what you will get from this resource. This was the case when we checked on the agency that worked us over so well. Don't forget, firstname.lastname@example.org if you are curious about what agency this was.
Another resource of confirmation is the State Attorney Generals Office in thye state where the agency you are considering is located. But, don't just check with the AG in the Capitol; most states have AG offices in other major cities Check the one in the home city of the agency as well. Check them all.
You can also consult with the Department of Family and Protective Services. This agency name may vary from state to state, but it is the licensing agency responsible for monitoring Adoption agencey's and will have records of complaints filed against an agency you may be inquiring about.
You might also consider checking with the States Secretary of State. I found complaints about our agency lodged here.
Incidentally, I found complaints about our agency all over Texas in various departments and ranging from #35.00 to #37,000.00.
If only I had done all of this work before we got snared in this trap.