Ben Elers, program director for Transparency International, a nongovernmental organization, said social media had given the average person powerful new tools to fight endemic corruption. “In the past, we tended to view corruption as this huge, monolithic problem that ordinary people couldn’t do anything about,” Mr. Elers said. “Now, people have new tools to identify it and demand change.”

Since no names are given on the sites, in part to avoid potential issues of libel and defamation, it is impossible to verify the reports, but Mr. Elers and others experienced in exposing corruption say many of them ring true.

They are threatening enough that when a rash of similar sites popped up in China last summer, the government stamped them out within a couple of weeks, contending they had failed to register with the authorities.

They are, however, only a reporting mechanism. “In their own right, they don’t change anything,” Mr. Elers said. “The critical thing is that mechanisms are developed to turn this online activity into offline change in the real world.”

Antony Ragui is hoping that happens in Kenya, where he started an ipaidabribe site in December. The site has gotten about thousands of hits since then and recorded about 470 bribery reports. The bribes are as varied as payments to make traffic infractions vanish from records and payments for admission to schools and for passports and identification documents.

“What if that person who paid a bribe to get a driver’s license because he failed his driving test hits your sister or your child?” Mr. Ragui said. “We have a huge issue of Somalis paying bribes to get passports and personal identity cards to come to Kenya — what if one of them is a terrorist who blows something up? The bribes may be small but the consequences may be big for you and me.”