Earlier quoted context omitted.
Legally they're fine because the responses were anonymous and none of the users would reasonably believe that their responses would remain completly private. Ethically (at least in my opinion) is the same, as long as they're kept anonymous and there's nothing personal or private in the responses they can use them for any reason. Especially because they were given in lieu of payment.
Are you saying that expecting any privacy is unreasonable these days?
2. In my opinion, posting completely anonymized responses is not a violation of privacy