If you'll humor me leaning into the steel man and addressing advertising-as-practiced i.e. ad-tech rather than advertising in the abstract sense:
Data collection is the big harm right now. Advertising companies have enormous databases on ~any individual's interests, political opinions, gender identity, and much more.
The immediate harm of all this data collection is that, while Google has good security practices, the average webshop or advertising middleman does not, and so data leaks are frequent. Stalkers and harassment groups as well scammers and other fraudsters already use such leaked data. This particular harm is in the here and now.
The big looming threat is: What happens when a government decides to tap into these databases. (Y'know. Like they do in China.)
Because right now, should a government ever want to, it can just call up Google, Facebook, whomever else, and ask: "Give us a list of everyone who meets these criteria".
This completely trivializes any kind of large scale oppression of the people. Pre-compiled lists of almost every political dissenter, with verticals across almost every topic imaginable.
It's no hypothetical either. During WWII, the Nazis seized civil registry records in order identify and kill people as part of the holocaust. There's no reason why any future authoritarian government won't do the same to the big ad-tech databases.
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For something in a lighter mood: The one general problem about advertising is that it's an industry prone to quite a lot of fraud. There's an inherent information asymmetry in that advertising agencies have a near-monopoly on not only the performance data, but also how it's gathered.
How many impressions did a video get? Only Facebook knows. What's an impression? Only Facebook knows. And why would they ever be honest about those two things to you, the advertising buyer?
As you pointed out, very simple registries are already more than sufficient for government oppression. Detailed data that Facebook collects, like which brand of dog food you prefer, is neither necessary or even helpful for government oppression. The ads data is not even 1% as useful to them as things like telephone records, which the telephone companies will happily send as required by law
Data collection is the big harm right now. Advertising companies have enormous databases on ~any individual's interests, political opinions, gender identity, and much more.
The immediate harm of all this data collection is that, while Google has good security practices, the average webshop or advertising middleman does not, and so data leaks are frequent. Stalkers and harassment groups as well scammers and other fraudsters already use such leaked data. This particular harm is in the here and now.
The big looming threat is: What happens when a government decides to tap into these databases. (Y'know. Like they do in China.)
Because right now, should a government ever want to, it can just call up Google, Facebook, whomever else, and ask: "Give us a list of everyone who meets these criteria".
This completely trivializes any kind of large scale oppression of the people. Pre-compiled lists of almost every political dissenter, with verticals across almost every topic imaginable.
It's no hypothetical either. During WWII, the Nazis seized civil registry records in order identify and kill people as part of the holocaust. There's no reason why any future authoritarian government won't do the same to the big ad-tech databases.
---
For something in a lighter mood: The one general problem about advertising is that it's an industry prone to quite a lot of fraud. There's an inherent information asymmetry in that advertising agencies have a near-monopoly on not only the performance data, but also how it's gathered.
How many impressions did a video get? Only Facebook knows. What's an impression? Only Facebook knows. And why would they ever be honest about those two things to you, the advertising buyer?