The unit, now called (at)Walmartlabs, suggested that the retailer give juicers prominent display for the holidays last year, after a movie about an obese man who lost weight on a juice diet started trending online. Wal-Mart declined to give examples of how it used online chatter this holiday season but said it's slowly playing a bigger role in product decisions.That's critical because companies are realizing shopping behavior is often more influenced by what's happening in pop culture, rather than their own past shopping patterns, said Shernaz Daver, a spokeswoman for (at)Walmartlabs. "Social media has enabled us to understand intent," she said. Melinda Vitale Shaw, owner of the two-store MeLinda's Fine Gifts in Picayune, Miss., is using the same concepts as the world's biggest retailer. Since setting up a Facebook page in 2010, she's used it as a sounding board for what to stock in her stores. In the south, for example, it's common for people to change the decorative flags outside their homes depending on the season or the holiday. To get a better sense of what type of decorative flags might sell well next year, Vitale Shaw recently asked fans to post about the designs they were currently flying, or what they wished they were flying. She was surprised to see several comments about snowman flags, since it doesn't snow much in the south. Even though Facebook sometimes proves her business instincts wrong, she called the site "a true retailer's friend." In a more unusual case, the outdoor retailer Gander Mountain is handing the reins over to fans on social media. The chain, based in St. Paul, Minn., is running a promotion that lets customers determine the price of its products. Every Thursday during the holiday season, customers can push down the price on five selected items by sharing them on Facebook or Twitter. The more shares an item gets, the lower the price goes; discounts start at 10 percent but can go as high as 50 percent. Shoppers can jump in and buy the items at any point, or wait for a lower discount but risk that the store will run out of the items.