The Los Angeles MongoDB User Group was founded by Joe Devon in 2011 and has grown to over 400 members, thanks to his leadership. Devon started organizing user groups after moving to Los Angeles from New York City, where there were already several meetups available. He began hosting meetups at Panera Bread and eventually gained a following of regular attendees who took over the group. The LA MongoDB User Group has been successful due to its focus on serving the community, providing substance in talks, and partnering with 10gen for support. Devon's advice for starting a user group includes being proactive, clear about logistics, and providing value to attendees. He also shares his enthusiasm for new technologies, such as MongoDB, and encourages others to follow their passions and break new ground.