Social media, especially Facebook and YouTube, have become ubiquitous. Facebook now has over 800 million active users and earned over $3 billion in ad revenue in 2011 alone. While social media is noisy and subject to trends, it clearly influences user behavior. Social recommendations and sharing improve users' perception and experience of content and increase click-through rates for emails. Social networks are also increasingly used to find local businesses. However, direct social commerce faces challenges around trust, privacy concerns, and personalization of experiences. More data is still needed to fully understand social media's impact on marketing and sales.