Facebook forced to disclose more information about its ad targeting

Good inquiry!

An interesting question with look alike audience seems to be if FB "decrypts" the md5-hashes of uploaded by a willing company of user names not matching FB user base - see shadow profiles.

Also which company uploaded their user base names (hashed) into FB and to which you belonged initially?

I think technically, the anonymity of md5 hashes regarding email-adresses is disputable. The Bavarian authority body does not accept FB hashing solutions because of the weak protection md5 offers, as we all know.