Research has begun to address the use of social media sites, such as Facebook and Twitter, for supplementing and enhancing classroom-based learning. However, the use of social media platforms for less formal learning has received little attention. Study One of this dissertation presents the results from semi-structured interviews with twenty-one users of the photo-sharing social media site Flickr about their Flickr use, focusing on how participants learn more about photography through their use of the site. Utilizing the communities of practice lens, findings illustrate how Flickr Groups function as communities of practice. Participants describe solitary and interactive learning strategies they employed which allowed them to advance their photographic knowledge and skills. The role of expertise emerged as an important factor in sharing knowledge about photography. Access to experts has been found to be a motivating factor for participation in online CoPs and expertise has also been linked to contribution in online communities. Study Two presents the results of an online survey of Flickr users (N = 200), which measured three key forms of participation in Flickr CoPs (photograph posting, commenting, and discussion board posts), photographic expertise, and personality traits. Findings revealed that user expertise predicts certain forms of Flickr CoP participation, including commenting and sharing knowledge. Personality traits were also found to predict user activities, such as commenting and asking questions. The combined findings of these studies demonstrate how social media can be used as a powerful learning tool and shed light on how users leverage site affordances for learning [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]