The Journal Impact Factor, calculated and published annually by Thomson Reuters, is the most influential metric in academic publishing. It is widely used to judge the performance of scientific journals and is still widely misapplied to assess individual scientists. Journal editors and publishers thought they know how to play the system - and lost. Other editors and publishers apparently didn't play the system - and lost, too.
To counteract Impact Factor manipulations by editors, in 2008 Thomson Reuters started suppressing journals with abundant journal self-citations and excluding them from the Journal Citation Reports® for two years. The number of banned journals rose from 9 in 2007 to 66 in 2012. Abundant journal self-citations can be caused by the nature of the journal or by unethical strategies of editors, such as coercive citations or citation cartels. Regardless of whether unethical behavior was involved, journals with excessive self-citations are suppressed by Thomson Reuters. While unethical behavior needs to be discouraged, depriving the accused journals of the benefit of the doubt can lead to unfair treatment.
(Extract from: KRELL, F.-T. 2014. Losing the numbers game: abundant journal self-citations put journals at risk for a life without Impact Factor. European Science Editing 40 (2): 36-38.)