Iran, like any other police state, has to be creative in finding ways to control troublesome foreign media. Iran has achieved a great deal of control over foreign news organizations by arresting and imprisoning female reporters. The most recent one arrested, Roxana Saberi had been working in the country for six years, reporting stories for NPR and BBC. These two news organizations have been more accommodating to the clerical dictatorship, than most. But there is so much wrong in Iran these days, that even NPR and the BBC will come up with stories that will offend some of the clerics, particularly the more radical ones. Since the radical faction control the secret police and many judges, it's not difficult to arrest and keep in prison, and even convict (usually for being a spy), foreign female journalists. For every foreign journalists you do this to, dozens are suitably terrified. Thus stories the clerics don't like will not be written, or will be toned down.
Eventually the more moderate, or sane, clerics usually convince the radicals to let the foreign journalist go. Although in one case, a female foreign journalist was beaten to death in prison before she could be released. In most cases, the journalists are let go and tossed out of the country.
In most cases, these women are of Iranian ancestry, and usually have dual citizenship. That means, when they are in Iran, they are considered Iranian citizens. Thus their other homeland (usually the U.S., Canada or Britain) can't do much for them. Western nations protest this shabby treatment of journalists. Most Iranians love that, as it publicizes what Iran does to journalists who report the wrong things. Iran treats its own wayward journalists the same way, and usually worse. Bloggers or others who publish something the clerics don't like can be beaten, jailed or killed. Iran claims to have a free press, as long as you don't offend or embarrass the clergy who run the nation.