  In the Twitter blogosphere, the number of followers is probably the most
basic and succinct quantity for measuring popularity of users. However, the
number of followers can be manipulated in various ways; we can even buy
follows. Therefore, alternative popularity measures for Twitter users on the
basis of, for example, users' tweets and retweets, have been developed. In the
present work, we take a purely network approach to this fundamental question.
First, we find that two relatively distinct types of users possessing a large
number of followers exist, in particular for Japanese, Russian, and Korean
users among the seven language groups that we examined. A first type of user
follows a small number of other users. A second type of user follows
approximately the same number of other users as the number of follows that the
user receives. Then, we compare local (i.e., egocentric) followership networks
around the two types of users with many followers. We show that the second
type, which is presumably uninfluential users despite its large number of
followers, is characterized by high link reciprocity, a large number of friends
(i.e., those whom a user follows) for the followers, followers' high link
reciprocity, large clustering coefficient, large fraction of the second type of
users among the followers, and a small PageRank. Our network-based results
support that the number of followers used alone is a misleading measure of
user's popularity. We propose that the number of friends, which is simple to
measure, also helps us to assess the popularity of Twitter users.
