I had my Facebook deactivated for 6 months, during which I visited Saudi Arabia and worked with a guy for three days. The main communication during this trip was WhatsApp.
Few weeks ago I reactivated my Facebook, few days later I found him as one of the recommended friends. I don’t have Facebook app on my phone so they can’t have access to my address book, but I have WhatsApp, which is owned by Facebook.
Today I had a friend asking me, how can she disable allowing Google to get access to her location. She said whenever she opens Google search she finds at the end of the page Google telling her where she is. When she opens Google maps it automatically opens on her neighborhood. She went so far to reinstalling windows but still couldn’t get rid of it.
I told her they are getting her location from her IP, and gave her a locate my IP link so she can get a better idea. And as for the Facebook case, I know how they got this guy, but not every Facebook user knows that WhatsApp is owned by Facebook and technically they can connect the missing pieces from Facebook to WhatsApp and the other way around.
With the explosion in data collection and ease of analyzing the data for smarter recommendations, users are losing control over what they are sharing not understanding how it can be used later. This leads to a bigger UX challenge where whenever a company is introducing a new feature specially in recommendation, it needs to reassure the user that their information is safe and there is nothing to worry about. Otherwise it is too creepy.