Comments and Likes are one of the key elements that make up the "social network" side of Facebook—without them, users are just shouting into a vacuum, but with them, they're connecting with friends and strangers alike, and voicing their opinions.
For the most part, working with Comments and Likes is little different from working with any other Graph API object—the methods and API requests are more or less the same, but it still helps to look into the specifics of working with these object types, find out where they can be applied, where they can be used, and how we can best integrate them into a Flex-based application.