A more concrete analogy would be if you donated to an egg or sperm bank, and found out later that the hospital had destroyed samples after checking the donors linkedin profiles for employment gaps.
If you would really like to turn my innocent quip into an something more inflamatory, I'd say a lack of informed consent by users about the use of their data, obtained by surveillance, used to impose opportunity costs on their reproductive prospects, structured around the commercial and political agenda of a company who makes addictive products - would be a pretty awful thing to countenance indeed.
I'm sure the lawyers and bioethicists have got it all sorted out.
Matching people based on their survieled unintentional preferences instead of their stated intentional ones seems helpful, except I'd propose that the combination of opacity and power difference ethically deprives the subjects of their intent.
They may have volunteered for the opportunity, but they have not volunteered to be chosen for. The selection bias inherent in secret data is the expression of the intent of the administrator, not the intent of the subjects.
Taking this beyond a quip wades much deeper into thorny ethical issues than is really useful on HN, but I hope this has emphasized the value of letting sleeping dogs lie.