It's a well-known conspiracy theory, but we've learned a few things over the past month about how Facebook works that might explain what happens when you mention products in person during a conversation, then see ads for that product pop-up in your feed.

I've had this happen myself. You're chatting with a friend in person or on the phone. Later that day or maybe over the next day or two, you start seeing ads pop up mysteriously for that exact same product. As an example, you might mention a new Airstream camper to a friend, and then suddenly you see an ad for that exact same model.

No one has ever really explained it, and Mark Zuckerberg flat-out denied it during his Congressional hearing last week. The beleaguered CEO said Facebook obviously uses your video camera and microphone when you stream or record a video, but denied any tampering when it comes to using a microphone to secretly listen to your conversations.

And yet--the conspiracy still exists.

And people are puzzled.

One theory is that it is all in our heads, it doesn't actually happen. We know Facebook does monitor our web searches. You search for Corn Flakes on Amazon and you see an ad, but it's an accepted practice (one that might not be so accepted in the future.) What about those times you mention Corn Flakes to a friend? Or talk about a new iPhone case to a friend? You say the specific name for a product ("Mophie") and suddenly you see an add for a Mophie case in your feed. You mention a new desk chair to a coworker. Then, ad ad pops up later. It feels like an evil overlord is monitoring everything we say and do.

It's a real headscratcher.

Or is it?

I have a new theory about how this works.

Many of the conspiracy theorists say they never, ever do a search for the product in question on their own, and I believe them. But, we know that Facebook also uses the searches and preferences of people you know as well. That came to light recently when Facebook revealed how Cambridge Analytica captured user data. It started with a survey of just 300,000 users, but the survey managed to read the data from the contacts of the survey participants, and the total number for the data leak is closer to 87 million.

I'm making an educated guess here, but the answer to the conspiracy about Facebook listening over a microphone on your phone or laptop may be much easier to explain.

I doubt Facebook is listening to anything. That would be downright illegal. It's wiretapping. But all of those friends and family members? The ones who you are talking to us in person or on the phone? My theory is that they are then then doing web searches for those products. They get back to their desk or end the call with you, and search for Mophie. They search for that cool new Airstream, they look into that new USB cable on Amazon.

This is likely not an isolated incident, either. If you're like me, you maybe chat about a new product over Messenger, and you mention it to multiple people, who then do a search. It's how we do things these days. You hear about it, then you search. My theory is that Facebook knows what you friends are searching for, and then they start feeding you those ads. It works because Facebook knows you are interacting with a small group of people. The "friends" you talk to in person are at the top of the pile for Facebook, way above the virtual friends. Facebook also knows that. If three close friends search for a Mophie case after talking to you in person or on chat, you'll see the ads.

Do you think this theory holds water? Do you have another one that makes more sense? I'd love to hear your thoughts so we can figure this one out.

Because, Facebook reps? They will say no comment. That's no theory.