Last month you probably told a friend which shoes run small, and the company that makes them will never know you said it. 95% of what people say about brands happens where the brand can't see it. Tagging was the main sensor brands ever had, and it worked when people found products through search and feeds, because the post that moved a sale usually carried the @. Then more of the buying conversation moved into the comments section. A creator holds up a shoe on camera, says the name out loud,…