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Anonymized data generally is not very anonymous. You can only trust that data is actually anonymous if there exists no non-anonymous dataset with which you can cross reference the anonymized data, and you can guarantee that no such database will ever exist.

I'm willing to bet that many "anonymized" datasets are of the kind which could relatively easily be deanonymized, especially datasets which are frivolously used to make ads "funny".

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Sure, but what is harmful about the statement.

Dear person, who watched $show $number of times in one $time, $snarky_comment?

Netflix themselves might know who this person is, but there's no way anyone reading the tweet is going to be able to link it back to a specific person. Are you concerned that Netflix can query their own data?

What if you were the person who watched that show N times, and then saw that ad? It'd be a weird feeling, right?

That's an incredibly broad statement; we are talking about what movies people have watched on netflix. What possible non-anonymous dataset could you be cross referencing to de-anonymize it? Even if you could, who cares?

I just responded to my parent comment's premise:

> what is harmful about using anonymised data this way?

Whether it's harmful to use such data when it's not anonymous is a different discussion.

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