Tourists have been scrawling their names on noteworthy objects since the dawn of travel. Young mainland boy Ding Jinhao was following the well-worn, but unlawful, practice years ago when he scratched characters into a 3,500-year-old pillar while visiting a temple in the Egyptian city of Luxor with his parents. He got away with the vandalism at the time, but it has come back to haunt him after being noticed by another Chinese visitor, who posted a photograph of it on microblogs. His parents have had to come forward tearfully to apologise after he was publicly named and shamed, his personal details having been spread throughout the blogosphere amid a storm of online outrage.

This is citizen justice mainland-style, one of the few ways authorities allow people to openly express their views. Chinese tourists have a bad reputation for the uncouth and uneducated habits of a tiny minority, so it is natural that microbloggers would want to make an example of lawbreakers. But while there should be a public discussion and debate, it is not the job of citizens to be judge and jury. While the boy needs to be told he has done wrong, so that he and others do not deface property at home and abroad when they travel, there is no good reason in the circumstances that someone so young - he is now only 15 - should be disgraced and humiliated in such a way.

Microblogs are a valuable form of communication. That is especially so given the lack of a free and independent media. The unmasking of corrupt officials through information spread among users has made that obvious. But the lack of a moderating filter means that mischief-makers and the unthinking can easily destroy lives and careers.