Twitter mobs on their own are indeed mostly harmless. Employers and other organizations that can have an actual impact on the target of the mob and who are complicit with it to avoid the possibility of making the life of PR people more difficult by having to defend the distinction between corporation and the personal opinions of low level employees are not.

Of course both sides are guilty of that and they basically crib from each other's playbook in the spirit of "having them taste their own medicine". In the end it it is never what one would call civilized discourse, no matter who is doing it and who you disagree with.