Meanwhile the NFL has been running the "Together We Make Football" campaign since 2013 as a way for fans to submit their personal stories through videos and essays. After uploading their tales to a website, users can share them through social media.  Specially selected stories have been turned into short films by NFL Films, segments on the "Today Show," and some winners have gotten tickets to the Super Bowl. During the past two years, the NFL said they have had more than 13,000 pieces submitted, leading to more than 2 million video views online.  NFL senior vice president of marketing Jamie Weston said Together We Make Football started because the league wanted to find a way to connect with their broad range of fans, not because they were jumping on the UGC bandwagon.  "We have 193 million fans from 5 to 95," she explained. "[UCG] works because it's authentic."  This year the NFL is bringing back "Together We Make Football," but focusing on asking fans to submit stories about how football inspires them. They will be renewing their partnership with the "Today Show," allowing some stories to be shared through the program. The NFL also signed a multi-year partnership deal with Twitter on Monday to seed official video and multimedia content on the platform. Brands can advertise on the content, especially those desiring to reach a youthful social media audience.  Read MoreCramer: NFL deal good for Twitter—here's why  One benefit to UGC is that it can be more cost effective, considering that most of the marketing materials are made for free by the fans. Using UGC also allows sports leagues and teams to tap into live moments and create content when they may not immediately have the broadcast rights to repurpose that content in a social space, Carey added.  "With Instagram, Twitter and Snapchat, you can allow the user to produce this content that isn't necessarily the game itself, but it still serves the purpose of promoting the game," he said.  However, Carey points out that in order to make sure it's an effective campaign and reaching the right audience, there's still a lot of effort from agencies and leagues to make sure participation is the kind of participation they want.  "The nature of today's social ecosystem just lends itself so well to being able to tell stories that are in the moment," he said. "We're at a point where we want to share those feelings in real time and share them with a mass audience. That resonates with sports and the sports fan, and marketers want to address those fans."
Sports leagues such as the NFL and MLB are relying on online user generated content for their marketing campaigns.