When you Google Xenophobia or Johannesburg Violence you come across plenty of assessments for why this is happening. 9/10 miss the point. The clue behind this mob behaviour is that in every instance it is associated with looting, with ordinary people running around with someone elses stuff. That speaks volumes. It's a zero sum game mentality - us or you, you go (or die) and we get what you leave behind.
This is difficult for people to understand who have cars and televisions. When you see people squabbling over a stolen bag of flour, messing the snowy powder over themselves in the tug of war, it begins more obvious just how desperate the poverty must be in some of these areas. And many of the poor are suffering the highest levels of AIDS attrition. Commonly, AIDS lays waste to those old enough to work - parents. And there have been alarming reports of large numbers of youths making up these mobs.
So there you have it: poverty - which induces resentment - Aids - which induces desperation - an influx of foreigners - which provides a convenient target (for now) - ongoing price increases and Zimbabwe's continuous decline - providing a combined sense of hopelessness and fear.
My concern is that as inflationary pressures increase, this mob violence will spill over into ordinary suburbia. Its the have nots (and there are millions) against the haves.