The author of that 2009 post remarks:
At least back in the day, members of lynch mobs had to get off their fat asses and actually meet the person face to face (or sometimes face to mask) in order to terrorize them. Now all they need is some limited computer abilities and a social network to conduct their dirty work.It is truly sick. And Tumblr must be held accountable - what these Tumblr people are doing is writing anonymously about what people on Facebook have said - and Facebook makes users provide their real names. The named vs. anonymous balance of power is obvious, and there is an obvious potential for abuse, although no doubt nothing will be done until somebody is killed thanks to lies promoted through an anonymous Tumblr mob.
People have already been threatened and attacked thanks to Internet mobs: From flash mob to lynch mob
The most concerning aspect of mobbing, though, is the way large groups of people can be mobilized to attack a perceived transgressor without their accusers providing any real evidence of their guilt. On the Internet, the mob can be judge and jury.
Although some people are making money through advice on dealing with online smear campaigns.
Internet Defamation Law Blog