"Why were most of those killed in the earthquake children?" one post asked Thursday on FanFou, a microblogging site.
"How many donations will really reach the disaster area? This is doubtful," read another.
China is now home to the world's largest number of Internet and mobile phone users, and their hunger for quake news is forcing the government to let information flow in ways it hasn't before.
A fast-moving network of text messages, instant messages and blogs has been a powerful source of firsthand accounts of the disaster, as well as pleas for help and even passionate criticism of rescue efforts.
"I don't want to use the word transparent, but it's less censored, an almost free flow of discussion," said Xiao Qiang, a journalism professor at the University of California, Berkeley, and director of the China Internet Project, which monitors and translates Chinese Web sites.
China is well known for controlling the flow of information.
"We didn't know that hundreds of thousands of lives passed away during the Tangshan earthquake in 1976 until many years after the disaster took place," sociologist Zheng Yefu said in a commentary last week in the Southern Metropolis News.
But word about Monday's magnitude 7.9 quake spread quickly on Web sites and microblogging services, in which users share short bursts of information through text and instant messages. The services also publish the messages online.
Read article - 'China allows bloggers, others to spread quake news'