I endorse, 100%, the following posts regarding the "mob justice" surrounding a Minnesota dentist who killed a protected Lion in Zimbabwe: Max Fischer at Vox, Kevin Drum at Mother Jones, and Clark at Popehat. Mob justice is not a good thing. It's not a good thing when imposed upon those who "deserve" it, and it's not a good thing because it is exceptionally poor at accurately identifying desert.
One difficulty surrounding internet outrage mobs, picked up on by Kevin Drum, is that they are often comprised of an infinite-iteration of individualized reactions which, taken in isolation, may be perfectly reasonable and measured expressions of outrage. Not all, of course -- even at an individual level threats of violence or vandalism would be unacceptable. But sometimes its a problem of multiplier. There's obviously nothing wrong with being upset that someone killed a beloved charismatic megafauna. Nor is there anything wrong with being harshly critical of an idiotic newspaper column, or taking umbrage at a crass and offensive tweet. The problem, of course, is there is a huge difference between a few people doing that and millions of people doing it. A controversy which might have been localized to a particular community, and blown over in a couple of days (potentially with offender and aggrieved persons being able to work out an acceptable resolution in person), now are massive international stories that can decimate lives and livelihoods. No individual member of the mob feels like they're doing anything untoward, but the aggregated effect is completely morally indefensible. The problem lies in the balance -- how do we as a collectivity express the "right" amount of outrage, when "amount" is determined largely by just how many voices are contributing to the choir.
I don't have an answer to that question, exactly. I think there are some markers to be on the lookout for, including whether the target is a public persona and whether the focus of the internet narrative is to promote the normal workings of the legal system rather than impose a form of vigilantism. But I do agree with Fischer when he says that mob justice "is not primarily about punishing the crime or the criminal, but rather about indulging the outrage of the mob and its thirst for vengeance." I've written about similar themes in my "Criticism as Punishment" post, and I refer back to it here. When we -- either as a legal collectivity or as a mass of private individuals -- seek to use "punishment" as a mechanism for expressing our own moral outrage, there is an exceptionally high potential for abuse. The next time one (and I include myself in this) think of joining in a chorus of outrage, pause and think whether one's contribution is primarily about correcting the wrong, or about signaling you're in the right.