I don't disagree that Facebook ads might work for certain product ("Check your IQ online!") but for a lot of product, they are never going to match up to search-linked advertising. Facebook can target ad by demographic (you're a teenager, you like skateboarding) whereas Google can target an active buying moment (you're searching for a new helmet.) The former is more similar to the old paradigm of television advertising at target demos than the new world of targeting actual purchasing behavior as it happens.