What if Amazon makes a full-blown entry into the advertising business, like Google

Today I wondered something - Amazon is already a powerhouse in online selling. It knows its customers' tastes. It knows the pulse of the public. It knows what sells and what doesn't. What if Amazon entered the online ads business too, just like Google? Amazon would not only show you targeted ads, it would also take you to Amazon's websites to complete the transaction [Google currently only serves ads, but doesn't allow/host actual transactions itself]. The prospect of Amazon offering advertising and retailing businesses in a combined form looks so powerful, it's almost scary.