There was a point a year or two ago where everyone was recounting these stories of how AI targeted advertising was terrifyingly accurate, it could tell you were pregnant before you found out for yourself, etc. At the time I was routinely opening YouTube with cookies disabled and getting suggested YouTube generated categories with a super low hit rate, stuff like "Recipes" that would be filled with nothing but general interest food videos (i.e. "you won't believe what we found at this market", "we made the largest burrito ever", never with any instructions), "Metal Music" containing a single acoustic cover a metal song and half a dozen EDM tracks or "Role Playing Games" stocked to the brim with Fortnite videos.

I just checked now and it's better than it was but there's still a "DIY" category containing one DIY video, a Japanese cooking tutorial and a video of somebody putting iPads in a bucket of slime. I'm not sure I have very much faith in their ability to deeply infer things about me from a limited dataset when they can't identify videos with ingredients in the description or sort music into genres given the set of all music (and millions of comments on it) to work with.

If you use Twitter, you can see the list of your supposed interests they have inferred from your activity on their own site. They have so much firsthand user data, but my results at least are so bad. Of almost a thousand topics, less than half are even remotely relevant to me. My supposed interests include people I've blocked, keywords I've muted, and non sequiturs like "cake", "water", and "hello".

https://twitter.com/settings/your_twitter_data/twitter_inter...

If you use Chrome, check out the "How your ads are personalized" page. It gives you a glimpse of how accurate Google's targeting is based on all the data they've collected.

I went to a great Google Fireside Chat with Michal Kosinski on data privacy. He said that the only way to get around big data is to spread misinformation. Chose the opposite of your tastes, search for things you don't like, etc. https://www.youtube.com/watch?v=VUwBcTgzbtU