A similar indirect way can be used to extract information out of Google's database. For example, launch an ad-campaign for any product, directed at people who love cats. Now if people click on the ad and buy the product, you know they must love cats.
This might seem like a brilliant idea, but you'll run out of money before you map all people for all things.
If you have so much money (spit balling here), you could buy google itself I think
There are easier ways to get data on people like their social profiles, and other online breadcrumbs like yelp reviews, any digital footprint really.
Another way is to buy databases of people. People have databases of HNIs, etc that you can purchase. This of course doesn't lend itself to much analysis but if the main purpose was to market to them or something like that, then databases work best :)
