Ad targeting. Google+ is designed to power ad targeting, and for that it only needs you to sign up once. This lets it combine the biographical information you initially enter such as age, gender, education, employers, and places you’ve lived with your activity on Search, Gmail, Maps and all its other products to create an accurate identity profile. And this powers targeting of more relevant ads it can charge more for.So despite comScore showing that the average Google+ user only spends 3 minutes per month on Google+, VP Bradley Horowitz wasn’t lying when he told the Wall Street J...