> Facebook works directly with six data brokers, all of which allow you to opt out from their sharing of your personal data, everything from your email to your purchase history.

And that sort of explains everything.

I kept wondering how the info that keep to the Google-verse (search, Gmail) makes it to Facebook. Now I know.

Does it mean that Google collaborates with these data brokers? While it doesn't harm them directly, it seems like a myopic thing to do, arming a company that may undercut your sole major source of income. Yes, I imagine they take it directly from the device, but doesn't Google have control over the Android internals?

Also, I am in somewhat unique position. Being a Microsoft zealot, I still carry a Windows phone (v8.1) with slowly dying services. I almost don't use Facebook yet I still get these too relevant ads, mostly according to what I google on my desktop.