Search has long ruled the roost when it comes to e-commerce. Google has reaped billions thanks to its role as the de facto starting point of the process. Now, along comes social media. Many true believers say social will overtake search as the way people discover products and content. Maybe. For now, search still dominates, but social media is clearly emerging as an important complement, as evidenced by a recent study conducted by Comscore and GroupM. View the study here