3. Uses you as the target audience for the advertisements.
If you ever search for a thing you want to buy over Facebook you might forget it after some time. But Facebook never forgets. It is just going to keep asking you indirectly to buy those products even 4 months later. You will be getting related ads on the right side of the pages you visit. Even if you have that product in your home already as you bought it long ago it is kind of enforcement Facebook implies. The cookies that most websites have embedded in them would be guilty of this but it is only Facebook that has the audacity and the shamelessness to keep posting these on a regular basis to your timeline and whatever you view. You might just be ashamed of what is being recommended to you in front of a friend.