What you're looking at is a visualization of a sample of Twitter @mentions on one day in late June. Each vertex is a Twitter account. Each directed edge is a mention of one Twitter account by another. You can see some accounts which get mentioned a lot (lots of inbound arrows to a central point) and accounts which do a lot of mentioning (lots of outbound arrows from a central point; these are mainly automata).
I find it absolutely captivating to explore. It's like a safari of conversational molecules.
Coming soon: more details about how I generated this visualization, and how you can produce your own.