No one imagines for a second that two Australian radio disc jockeys contemplated, or intended, that a nurse, the victim of one of their ''pranks'', would commit suicide. They are themselves presumably devastated, and that attention is being given to their psychological vulnerability is quite understandable, as is the new sensitivity of their management, given the enormous emotional backlash.

Who can ever fully understand or anticipate how other humans will respond to events; know why it is that some will engage in self-harm, or what the complex of causes behind such incidents are? Those inclined to rationalise such tragedies will add that prankishness, ''taking the piss'', or piercing the pomposities of the self-important or the ridiculous has long been an international sport, one that has given many hours of simple pleasure to the crowd, and that the best solutions are not necessarily bans or the criminalisation of fun.

Perhaps, but those who think this should also heed the public fury and the anger of the crowd, even as they say, defensively, that some of this anger may come from the personal guilt of having laughed at the original joke. This is in much the same way that popular fury about an over-intrusive press and at the activities of paparazzi after the death of Diana, Princess of Wales, was most likely to come from those who had earlier been most avid to buy and devour the results of such intrusions, and to savour the gossip and tittle-tattle about her.

Yet the death of the nurse Jacintha Saldanha has an additional ingredient. She was a mere member of the public, even if one thrust by events into an unwelcome public eye. By contrast Diana was a public figure, a person who had longed flirted with, and enjoyed, publicity of a certain sort but found herself unable to manage and control it. There is a real difference.

Those who devised the current prank may argue that the real butts of their joke were people like Diana - such as members of the royal family they were impersonating - not people such as the nurse. She came to be involved only because she was working at the hospital into which the Duchess of Cambridge had been admitted.

Yet it was that nurse, and the other one who took the call, who were in fact the real butt of the joke. She took a call at its face value, and responded much as one might have expected her to had the call been genuine. She was the one made to look stupid, at whom the world laughed. Hers was the humiliation. No doubt security people responsible for the royal family were annoyed at some (very slight) evidence of a weakness in their screen. Perhaps some royals, or royal devotees, were incensed at the lese majeste and impertinence of these cheeky Australian DJs. But the one whose mickey was taken was an ordinary person doing her job. Not only the DJs, but all the others who thought the prank was hilarious, were having royal and cruel fun at her discomfort. The crowd ever has a taste for impersonal cruelty and probably never actually gave a thought to how she might have felt.

There is a world of difference between that and having fun at the expense of a public official administering a silly policy, or a public figure with an inflated view of him or herself. They are, at least to an extent, volunteers. Ideally, there should be some proportion to the taking down compared with the putting up - a fact reflected in the widespread distaste by most citizens for the mass public exposure of small-scale crooks by stalking infotainment reporters. In some cases, moreover, the person made to look ridiculous is not the person carrying out the policy but the one who has loudly made it. It was, for example, the NSW Police Commissioner Andrew Scipione, and not any young constables, who was made to look an idiot by the antics of the ABC's Chaser program during the APEC conference in 2007, perhaps all the more so when his anger at his humiliation led to any number of pompous and silly responses. Perhaps it is unkind to reveal his character to the world, but it goes with his job and his salary, and those who think it would be fun to take him down a peg or two are at least picking on someone of greater size.

This is not the case when one plays a trick on a mere member of the public, or some essentially anonymous person caught by accident in newsworthy events. Put simply, it's cruel. The DJs may not have sufficiently appreciated this, but the public seems to. But that very public and very hostile reaction may show why the answer is not some ridiculous law seeking to distinguish between the ''good'' prank and the ''bad'' one, no doubt to be defined, long after the event, by a bench of dour judges. In the field of commercial radio, marked lapses of taste have commercial consequences. Ask Alan Jones.