How they track
No, Facebook didn?t hear your conversation. They are just so good at tracking you in other ways that it can feel that way.
We know that Facebook surveils our online behaviors: i.e., what websites we visit, what terms we search for, what we purchase online, etc. These tracking methods (which get extremely sophisticated beyond what we?re describing here) have a direct influence on the ads that we see.
In the case of the conversation with the friend, we can thank location tracking for that. Even when one is not signed in to the app, Facebook (given permission by the user) can track the location of our mobile phones.
Therefore, Facebook was able to determine that you and the friend were in the same location at the party. If the friend had previously had any online interaction with Yummy Time, then there is your connection. Facebook knows you?re friends on Facebook. It knows you were together. If that friend is bringing up Yummy Time, it?s likely that he or she has had some kind of recent interaction with it?Googling it, visiting the website, etc. Even if the mentioned product was one your friend purchased in a store, Facebook location tracking can be privy to the fact that your friend was at said store.
Let?s take it a step further. Even if your friend (Friend A) had only had a conversation about Yummy Time with another friend (Friend B), then Friend A could have been the one on the receiving end of the ad prior to talking about it with you. That?s enough for Facebook to try the ad with you as well.
In other words?
Beyond just being together, Facebook?s algorithm compares your interests, demographics, places you?ve been, groups you?re a part of, hashtags you follow (the list goes on) to that of your friend. If you and your friend are similar, and the friend has already left a trail of breadcrumbs to that product, then Facebook will serve you up an ad to see if you feel the same.