The obvious reason is that your friends are searching for things. When you talk to your friends and your friend mentions that he's going through a divorce, the odds are great that he's looked up a divorce lawyer online, because you're friends, FB figures you'd be interested in the same thing and starts serving you ads for divorce attorneys.

Or if your friend is renovating his house and does a search for new cabinets, you'll see cabinets show up in your ads. And you won't think anything about it until you talk to your friend about his renovations. Then you get home, and your FB is full of renovation ads.

Never attribute to malice or competence (voice fingerprinting for ad targeting )what can adequately be explained by a stupid algorithm ("my friends and I must like the same things" ad targeting).