The people in question are Alex Leavitt with Evan Burchard, David Fisher, & Sam Gilbert who created a report on the Web Ecology Project website titled:

Researching Quantized Social Interaction

The Influentials

Sounds complicated right?  Well to be truthful, it is complicated, at least to perfrom the research but its not hard to understand.  What the researchers did was:

Using a new methodology based on the content and responses of 12 popular users, we determined measurements of relative influence on Twitter.

We examined an ecosystem of 134,654 tweets, 15,866,629 followers, and 899,773 followees, and in response to the 2,143 tweets generated by these 12 users over a 10-day period, we collected 90,130 responses published by other users.

Basically they took 12 popular twitter users, looked at all their “tweets” gauged how many people reacted and either responded and /or corresponded that information over the 10 day period and produced an influence scale. (Grats to @chrisbrogan for hitting so high on the list, even though MC Hammer made it higher :P).

The report goes into greater depth (stop reading this summary and go read the report already) about the meaning of influence and offers some insight into the methods and actions involved in creating or gaining influence based on the twitter accounts studied.  Some insightful stuff.