Edit: for fun I checked out Adam's twitter posts -- and have no respect left at all.
That is very obviously untrue, and makes me wonder whether you read OP at all. Do you think only physical harm matters? The public nature of accusations and ensuing arguments can have a very significant effect on business/career prospects, personal relationships, etc. Even if you successfully prove that the accusations are false, people's impressions are colored by the acrimony itself. There's another story on HN right now about collusion rings in academic reviewing, which demonstrates this effect. This could do huge damage to many people's academic careers, regardless of guilt or innocence or which side they're on.
If you have never known anyone that this happened to, count yourself lucky. Most people who have reached any level of prominence in any field have probably seen it happen to a friend. Pretending that things aren't real unless they've happened to you is kind of noxious.
Let me be clear: there are multiple actual murders and lynch mobs that were the direct result of someone starting a rumor online and it snowballing from there.
How many of those are acceptable? You're dismissing this with "oh chucks most times they are right as opposed to always wrong" when we aren't arguing they are never right.
That's not what I gathered from the parent comment and it's not what "mobs do cause harm" mean, which is why I was confused by your rebuttal.
> I tend to think that accusations are usually well-intentioned and well-founded.
That might be the case, but we still have to deal with the times they aren't.
Mobs do cause harm. Cars do kill.