Specifically, I am interested in tangible examples.
The one thing I got from your post is: Meta can target you to deliver better ads.
If you have other specific examples of what else can happen, please elaborate. I am curious
I can see that happening in the future albeit with a low probability in the Western World at least. Of course you never know
Western democracy doesn't help much when a higher up wants to get you.
And then there are all the crazy bastards beating up people for their religion or their sexual orientation. It's been shown that Facebook leaks some personal data to advertisers with carefully crafted campaigns.
And if that doesn't worry you, there's also all the fraud that is spread via Facebook ads: "Better Ads" means "More convincing cons". Con men use ad targeting to deliver exactly the kind of fraud you are most likely to fall for. A relative of mine fell for a finance scam -- it seemed perfectly legit, and thanks to Facebooks accurate targeting the campaign was delivered exactly to the right person that would fall for it.
Don't give them your data.
Ok, a specific example: by a weird twist of fate, my country outlawed abortion (in most cases). Currently it's easy for affected women to travel somewhere and get help. Some people don't like it. With widespread tracking, it will be possible to target and punish women for breaking the law by getting abortion.
I want no ads in my life, ever.
When I need to buy something I look for research, reviews, competition, people who actually used the thing for some time and comment on the thing's weaknesses.
I want to control when I start being interested in something, and when I stop also.
When I need to buy something I need knowledge (weaknesses) and control. Advertisements are exactly the opposite of that.
So... no ad can ever be a good ad for me. Period.
We know that Meta tracks everything you do in a pretty invasive manner. We know they use this data to target ads, and while they claim not to share data with advertisers, we do know that people have figured out ways to leak some of that data.
Since they share data with a lot of 3rd party tracking companies, we would have to trust all of them to keep our data safe. It is highly likely that some of these companies employ malicious actors.
Now, maybe you think you have nothing to hide. But the political landscape changes all the time, and things that were legal one day might be criminalised the next day, or some terrorist organisation gets a hand on your data and figures that you are an enemy of their god for some reason, ...
The only way to protect against these things is to not store the data in the first place.