[chancho]

The more targeted the advertising, the more effective and therefore valuable it is.

But it's still hard to know what people want or need to buy right now

They can (and do) personalize it somewhat, but just aren't as well-placed as facebook, because they aren't as close to the user (people). People are ultimately where the money comes from. That's how advertisers get it.

So who's information is more valuable? Facebook's because they know more about you overall (your friends, your habits etc.) or Google's because they know what you want right now (because you just entered it right fucking there in the search box)

I'm leaning toward Google. If someone has a problem, they go to Google to search for ways to solve it, and as you point out, that's precisely when they're most amenable to advertising. People go to Facebook to connect with other people. Advertising will always be noise there. (Stupid mindless games notwithstanding.)