You should be able to convert this into an experiment. Find an off-the-beat market and start talking about it in the presence of your phone (and maybe with the

You should be able to convert this into an experiment. Find an off-the-beat market and start talking about it in the presence of your phone (and maybe with the app open, don't know the particulars of when the app can activate the microphone). If an ad for a product in the space appears it would confirm the hypothesis that FB is listening in.