On the other hand, we now know that Facebook is in essence a contractor for delivering targeted advertising. (Meaning, receiving and/or sharing any messages is

On the other hand, we now know that Facebook is in essence a contractor for delivering targeted advertising. (Meaning, receiving and/or sharing any messages is just an accidental side effect of this objective.) ;-) More seriously, I don't think that this will hold. The idea about contracts is about services that imply the use of certain data in order to fulfil the respective objective of a contract. (E.g., a postal service will need to handle the name of the recipient and the delivery address, as implied by the objective of the very contract.) Here, however, the extraction and use of personal data is not a side effect of the contract, it rather describes the objective of the contractor in its entirety. (Disclaimer: I'm not learned in the law, but actually Austrian, if this is of any help.)