Update | 5:31 p.m. A reader, Jon, writes to say that “a friend in Iran that I have been in touch with via Skype (which seems to work very well)” told him that a specific Web site, Gerdab.ir, is being used by the Iranian government to identify protesters by crowd-sourcing. The Lede has been unable to get the site to load to confirm this (and the site may be under attack from supporters of the protest movement), but the information passed on by the reader suggests that Iranians are being asked to study photographs of protesters taken at demonstrations and then turn them in to the authorities.
Later: A reader points out that Gerdab.ir is back up and is in fact running at least one page of photographs taken at protests, with the faces of 25 protesters circled, and an appeal for information on these people.
Also in passing, many of the blogs have been critical, mostly for good reason, of the mainstream cable outlets. They are reading the same thing as the blogs, but not doing the same due diligence that we expect of journalists. Today, it seems like CNN was played by the Iranian government. CNN made headlines everywhere with an interview with a woman describing a "bloody massacre" at a demo in front of the parliament building. Apparently, later reports suggest that it was bad and tense, and one person may have been killed, but not the bloodbath described in CNN's report. The Iranian government is using headlines like this to keep people off the street. Like the website above, it's intimidation.