1. The document discusses modeling user interactions in online social networks to solve real problems. It analyzes data from Twitter and Me2Day to classify different types of interactions and their relative strengths.
2. Different types of interactions were found to have different "interaction indexes" representing their relative impacts. For example, replies were found to have a higher index than retweets on Twitter.
3. The authors propose developing models of user relationships and interactions to help address problems like finding experts to follow on Twitter or detecting disconnected friendships on Me2Day. Future work would expand interaction ontologies and integrate more social network data.