I started getting tons of ads for elder law immediately after I started watching Better Call Saul. I watched them on VLC on Arch Linux and _acquired_ the files over a year earlier. I hadn't Googled it, visited any related pages or posted about watching it. A little while after I uninstalled the Facebook app they stopped.
I was very much on the "there must be another explanation" train, especially since it should be possible to notice a ton of bandwidth if they were streaming conversation audio.
But I've really never been able to figure that one out. If you've got an explanation for me I'd be really interested.