ABC's Jim Sciutto, reporting from Tehran, ran into trouble with police when his camera crew shot video with its very visible equipment. But he was able to shoot and send video from his cell phone, talk live on the air, and send messages to his Twitter page.
"We witnessed police spraying pepper gas into the eyes of peaceful female protesters," he said in one tweet.
In another: "Photos show at least 3 people shot and injured. AP photog confirms to ABC he saw one person killed."
Since, even under more peaceful circumstances, the Internet is largely an open, unmoderated forum, many postings were requests for information, and others were probably wrong. But a picture emerged of post-election anger, efforts to quell it notwithstanding.
"It is always a shame when a countries' cultural and political concerns lead to limits being placed on the opportunity for sharing and expression that the Internet provides," said Facebook's Schnitt.
The Associated Press contributed reporting for this story.