Michelle Moghtader lists seven reasons why Iranian democrats haven't reemerged in 2011. Gary Sick largely agrees, but adds that events in Syria could change the dynamic:
Syria may be the key for Iran. Not only is it the channel for Iran to maintain its strategic political and military relationship with Hezbollah in Lebanon, but it is also a possible template for Iranian domestic turmoil. If mass popular demonstrations eventually prove able to overthrow a crypto-Shiite (Allawi) political-military dictatorship in Syria, that will inevitably play back into Iranian internal politics.
The Dish 