Censorship invites abuse. In China, the widespread practice of Internet censorship means that lots of people are authorized to hand down censorship orders and lots more people naturally turn to censorship when something on the Internet bugs them. This week, Chinese authorities prosecuted an "Internet policeman" who took payments from companies in return for censoring unfavorable remarks about them on social media. He's accused of censoring more than 2,500 posts in return for over $300K in payments. He also collaborated with another official to censor critical remarks about government officials. It seems unlikely that Gu, the Internet policeman who was arrested, and Liu, his collaborator, were the only two censors-for-hire in the Chinese system.
Lest you think that this problem is uniquely Chinese, consider that when Wikileaks leaked the Great Firewall of Australia's blacklist, we learned that more the half the sites on the list didn't meet the censorship criteria. And when the Danish and Swedish blacklists were analyzed, it emerged that more than 98 percent of the sites blocked did not meet the official criteria for censorship. And in the UK, the national firewall once blocked all of Wikipedia.