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...