Thanks to Susan Scrupski:
Andre Pannison, a network scientist at the University of Turin, hauled out some network tools (and some clever thinking) to map one hour of Twitter activity at the time of Mubarak's resignation on Feb 11. It's worth reading Andre's post describing what he did. And it's really required viewing for those interested in how networks evolve. Such beautiful patterns emerge from the simple act of messaging.
And here are a few paragraphs of his explanation:
This is a preliminary result of the network of retweets with the hashtag #jan25 at February 11 2011, at the time of the announcement of Mubarak’s resignation. If you retweeted someone, or has been retweeted, it is possible that your username is one of these tinny points (or maybe a bigger one?).
To collect the network data, I used the Gephi Graph Streaming plugin, connected it to a Python web server I made myself. This web server works like a bridge, it connects to the Twitter Streaming API using the statuses/filter service and converts the users and retweets to nodes and edges in a network format that can be read by the Gephi Graph Streaming plugin. Nodes are twitter users, and links appear between the nodes A and B when B retweeted a message of A containing the hashtag #jan25.