Also see Twitter’s wiping tens of millions of accounts from its platform (Vox)
"The reform takes aim at a pervasive form of social media fraud. Many users have inflated their followers on Twitter or other services with automated or fake accounts, buying the appearance of social influence to bolster their political activism, business endeavors or entertainment careers.Battling Fake Accounts, Twitter to Slash Millions of Followers -- NYT
Twitter’s decision will have an immediate impact: Beginning on Thursday, many users, including those who have bought fake followers and any others who are followed by suspicious accounts, will see their follower numbers fall. While Twitter declined to provide an exact number of affected users, the company said it would strip tens of millions of questionable accounts from users’ followers. The move would reduce the total combined follower count on Twitter by about 6 percent — a substantial drop."