I'm surprised that everyone is so shocked by it!
Apps like Google maps record your every location, coffee shops you enter, where you live and work, where your family lives. They use your metadata to analyse your life. If you and another person both stop at the same location for a period of time (such as a film, dog park, bus stop), that will be sufficient for the algorithms to potentially assume a connection and 'suggest'.
It's not it 'might' be true, its absolutely true. If you don't like these features you should def get an andriod phone, limit your use of applications, individually go into each app and select highest privacy levels. Also, just use facebook on your home computer and not your phone.
If that all sounds too much and you want the convenience of all the features, accept that the price is your privacy.
EssentialHummus your computer ha an IP address, a bit like a street address for your device. Algorithms assume multiple email accounts with the same IP address are linked.
Also, don't get those voice recognition systems, they literally record every single thing you say. So if you have a conversation with with someone about say, truck hire, you will see ads next time you use your search engine. I'll probably see those ads just for writing this sentence.
And don't get that feature where your phone unlocks on seeing your face. If you were to be stopped by police for example, they would be able to just open your phone and look through it.
Get a VPN, if you don't know what that it is, look it up and get privacy literate. It's a whole new world to navigate.