Someone told me if you go to an adoption agency and they turn down your application for whatever reason, and you start with a new agency, but say you never used another, is there a way the new aagency can find out about the one who turned you down

Well, it depends on why you were turned down, I'm sure.

I doubt it's "blacklisting". I'm sure it's more that there is something lacking that would make you a good adoptive parent--the willingness to "share" your child with its birthparents, the attitude which you'll need to be a good adoptive parent, a background that is not up to par, lack of funds, etc.

There are SEVERAL reasons to be turned down by an adoption agency, and I don't doubt that most of them use much of the same criteria for approval.