[Ozzie_osman]

It's a little different. Targeting these days is more and more machine learning driven. So it's not really someone sitting down and saying "show an ad to anyone who stayed at a house with someone who bought this toothpaste". Rather, a bunch of data flows into Facebook and it uses those signals to decide who should see what. It's not a naive analyst. It's a statistical engine (and yes, that engine can sometimes be naive, and it's working off of really noisy data).

For example, any good Facebook marketer probably uses "lookalike audiences". You upload some existing customers and then tell Facebook to show ads to people who are "like" your customers. Facebook then used whatever data it has to find similar users (demographic, interest, geographic, behavior etc).

In fact, lookalikes can be so good that any good marketer also knows to _exclude_ existing customers from the lookalike audience (unless you're actually retargeting your existing customers).