Washington - The killing of a Zimbabwean lion by an American dentist is a vivid reminder of how, in this era of social media, it's a virtual jungle out there.

Big game hunter Walter Palmer joins a growing list of individuals -- famous and not so famous -- who have been publicly, even ruthlessly shamed on Twitter and Facebook, the village stocks of the 21st century.

"He needs to be extradited, charged and preferably hanged" for slaying game park lion Cecil, said animal rights group PETA in one particularly scathing tweet.

"I hope you burn in hell," echoed several other Twitter users as #CecilTheLion became this past week's hashtag du jour.

Stoning, torture, even being fed to the lions were further suggestions posted online as Palmer went to ground and Zimbabwe called for his extradition.

"Public shaming through social media is clearly a way that people in our society informally 'punish' those who violate the rules, even if the rules of our society aren't law," said Lori Brown, a sociology professor at Meredith College in North Carolina.

"It is similar to the public stocks and just like that kind of punishment, some are content with simply ridiculing the person, but others may want to throw things or even harm this person," she told AFP.

"So there is the dangerous or potentially cruel edge to this kind of public shaming."

Some have found themselves in the crosshairs of social media shaming by discovering the hard way that humor doesn't travel well in a 144-character tweet.

"Going to Africa. Hope I don't get AIDS. Just kidding. I'm white!" New York PR executive Justine Sacco famously quipped before flying off to Cape Town in 2013.

'Troublemaker'

Many of her 174 Twitter followers were friends, and she clearly identified herself in her online profile as a "troublemaker on the side" with a "loud laugh."

But Sacco instantly became a global laughing stock, awash in a tsunami of blistering tweets that only intensified when she got off her 11-hour flight, discovered what was happening and apologized.

Even businesses and charities jumped on the bandwagon. By one estimate Google made up to $468,000 off the Internet traffic it generated, according to British writer Jon Ronson.

"You can lead a good ethical life, but some bad phraseology in a tweet can overwhelm it all," said Ronson, author of "So You've Been Publicly Shamed," in a TED talk in London in June.

In a sense, the Internet has stirred a revival of medieval-style public humiliation, a fixture of puritanical 17th century American colonial life.

The difference is that shamers today can shame anonymously, behind the mask of bogus identities. And there is no need to turn up in person at the village green to join the baying mob.

New York University environmental studies professor Jennifer Jacquet said shaming has value as a useful tool for advancing political change and social reform.

But Jacquet, author of "Is Shame Necessary? New Uses for an Old Tool," wonders if 2015 is the year that shaming has reached its peak.

"We really do have this pile-up of victims where we go, 'Mmm, maybe we went a little overboard'," she told AFP in a telephone interview.

Here to stay

"Shame is never going to go away. I think the real question is how we use it in society to good ends that the general broader democracy can support."

Vanitha Swaminathan, a University of Pittsburgh marketing professor, said the reputational consequences of online shaming can be so severe that it may look out of proportion to whatever prompted it.

"On the flip side, the speed at which these transgressions achieve prominence and fade away suggests that while social media backlash may seem very harsh, social media's attention span is also narrow," she said.