Why's that? This isn't a zero sum game. You don't advertise only on Google or only on Facebook; as much as your budget allows, you advertise on every channel you can achieve a positive ROI on.
For any advertiser looking for a direct response, like a signup or purchase, I doubt anything Facebook can do would make the ROI better than advertising on search. No amount of demographic and interest targeting will make advertising to people as effective as advertising to intent. You can pay Google to send you people while they're in the process of looking for your product; Facebook doesn't do that.
A combination of tech expertise and marketing savvy are needed to reduce this problem. More analytic tools are available for Google Adwords than are available for Facebook ads.
See, the essence here is not to come up with a great algorithm. This is not a programming contest. But to create a system where everyone (publisher, advertiser, ad-network and customer) wins.
In this very early stage, the success of Facebook's Ad network should be measured only by one metric - ROI of Advertisers. And that number has to be consistently better than Google's.