This document summarizes a study that analyzed social networks on Twitter through hashtags. Two datasets were collected around the hashtags #iranelection and #michaeljackson over 24 hours each. Social network analysis was used to map interactions between users through replies and retweets. The results showed that #iranelection had more conversational tweets and engaged users, while #michaeljackson had more content tweets and less engaged users. Both networks exhibited scale-free properties with some highly connected central users. The discussion notes that retweets may promote new social practices and relationships online. Further research will analyze the networks over multiple days and examine if social tagging systems enable new forms of public engagement and sociability.