Sometimes people claim mob-based shaming of people (on say, Twitter) will make others act better. In reality, mob-based justice has all the hallmarks of ineffective punishment.
The selective, random attention is not how justice is supposed to work. Justice works best when it is swift and certain, the punishment is proportional to the crime, and the defendant gets a chance to make his or her case. That is why our justice system is, in theory, supposed to evaluate someone’s crimes — and the punishment they deserve — with objective factors, and use several checks and balances, such as juries and appeals, to make sure someone is treated fairly.
Mob justice denies almost every aspect of this process. The defendant’s case is almost never heard, or at least not taken very seriously. There is no check to the vicious online harassment that almost immediately takes hold on the internet. And who is targeted is almost entirely random, based solely on what story happens to go viral and trigger the mob.
Mob justice can’t do any of these things, because it’s not supposed to. The goal of the internet mob is to seek vengeance — and that means doing so at whatever means are necessary. (Source)