No one needs an introduction to YouTube, which is by far the largest social video site. The YouTube API was first released in 2005, which seems like a long time back in the API timeline. At the recently concluded Google I/O 2012, YouTube officially announced a series of new APIs and enhancements that focused on mobile video, user engagement and Analytics.
Video content is being increasingly accessed from mobile devices and since Android based devices are expected to form a significant percentage of that, YouTube has released an Android Player API that will help developers embed high-quality and fluid video playback into their applications. Check out the YouTube Android Player API session at Google I/O 2012.
YouTube Direct, which allows web site owners to build a community by allowing members to submit video footage, which you can then moderate and play has made it easier accept video submissions. You can now make use of an Uploader widget that you can customize and embed into your site via a few lines of script.
With large amounts of data comes Analytics. You can now avoid processing the archive of Analytics data that was provided as CSV files. Instead use the YouTube Analytics API, a RESTful API that allows you to extract out information that you need. We can surely expect some interesting analytics tools being built now by developers.