Police arrested Kristi Abrahams and her partner, Robert Smith, on Friday, on what would have been Kiesha's seventh birthday.

Since then, several Facebook groups have been set up in connection with the case. ''RIP Kiesha Abrahams'' has more than 30,000 members, one of whom wrote: ''RIP beautiful girl. You were taken too early but now you're safe and in a beautiful place where you'll get the care and love you deserve.''

But other groups have been set up around the theme of revenge and retribution. One group, which attracted more than 1000 members before it was shut down, called for the reintroduction of the death penalty. Members referred to Abrahams and Smith as ''low life dogs'', ''moles'' and ''sick, twisted maggots''.

Another group titled ''No death penalty for Kristi Abrahams, the bitch needs to suffer'' also attracted more than 1000 members before it was shut down. Members of that group referred to the pair as ''cannibals'', ''mutts'' and ''cowards'' and many described in detail the modes of torture they would like to inflict on the pair.

Why do these groups spring up and what appeal do they hold for those who visit them?

More to the point, do they play any valuable role in allowing for group catharsis and communal outpouring, or do they merely breed mob-mentality barbarism?

Looking back at the public response to the murders or abductions of other children, such as the missing English girl Madeleine McCann or the murdered English toddler James Bulger, we can see that in one sense there is nothing new about these witch-hunts. Whenever a missing, abused or murdered child is in the news, public sentiment unfolds in a seemingly out-of-control and yet highly scripted manner.

First there is shock and disbelief at what has occurred, followed by intense anger directed at those parties perceived as responsible. This is usually followed by criticisms directed at ''the system'' (often government departments and other groups responsible for child welfare come in for a beating) and calls for a review of some sort.

Finally, the legal system comes under scrutiny, particularly if punishments are perceived as too lenient. Eventually, the news cycle moves on.

What is different about the modern social media witch-hunt is that people no longer have to travel, pitchfork in hand, to the town centre to revel in mob hysteria. They can do so online, from their bedrooms.

In the past, authorities could break up mobs and order them to disperse. Now that responsibility falls to Facebook and the moment a group is shut down its members can quickly regroup elsewhere.

For all the emotive rhetoric surrounding specific cases, we do little to prevent child abuse or to prioritise early intervention. Aside from the woeful funding of the Department of Community Services (and social work in general), there is a disturbing level of complacency when it comes to intervention.

The Australian Institute of Health and Welfare estimates that about 33,000 Australian children suffered some form of abuse last year. Yet a survey of 22,000 people by the National Association for Prevention of Child Abuse and Neglect found more than half of Australians say they would turn a blind eye when confronted with signs of abuse.

They would do so for fear that they might be wrong (48 per cent), because it was not their business (42 per cent), because they would not know what to do (38 per cent) or because they did not want to admit that the abuse had happened (22 per cent). Only one person in three would contact the police if a child disclosed sexual abuse.

In other words, while certain individuals are all too eager to get up on their soapboxes after the fact, few of us would step up and take responsibility if we were presented with signs of abuse.

What a shame we cannot channel this emotional energy into something positive, such as lobbying for better violence education and prevention, rather than focusing on revenge.

Nina Funnell is a social commentator and freelance writer.