This means people tell it exactly what they want. Who cares what your relationship status is when I can see you type in "wedding ring" into a search box? Who cares where you like to eat in the past when you searched for "chinese food" on maps, and potentially even clicked on an ad for a restaurant?
This is called "intent" and it's incredibly powerful because you can advertise for exactly what a person is actually looking for at that moment. Inference (like Facebook likes and profile details) will never be as good for real-time targeting.