A sociologist maps the universe of Twitter apps

In recent years, services like Twitter have exploded. Perhaps to bring some sense to the dizzying array of applications available for users, one sociologist has mapped the “Twitterverse.”

I like this graphic. However, I would be curious to hear the greater purpose of this chart. Does it indicate the popularity of particular applications? Does it reflect the date such applications were made available? Or is this simply an informational chart meant to display the broad range of services available on Twitter?

Additionally, this chart is a reminder of the dizzying array of apps Twitter users can download. Sorting through all of the possible apps on Twitter or in other places (iPhone, Droid, etc.) could be a time-consuming process.