The image below represents the network of the last 100 tweets using the hashtag #aacrao10. The data was captured and the network was constructed using R. Thanks to Drew Conway for showing me how to do this.
(Click to enlarge)
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Labeled dots indicate users that used the specified hashtag while unlabeled dots indicate 'friends' of users that used the specified hashtag.The code also allows you to compute important network metrics such as measures of centrality that are helpful in key actor analysis.