Users can upload their own information, including recipes, address books and classified ads.

NPR: Google Base Poses a Dilemma for Businesses

Facebook is trying to address this challenge by improving the way ads are targeted to users.

WSJ: Facebook Earnings: Profit Rises Amid Growth in Mobile

Yahoo wants to prove the influence by comparing different ads in similar demographics, and comparing data from a server address, a zip code, and credit card info from a purchase.

FORBES: Yahoo, Kardashian & the Spectrum of Engagement