That is a good point.
Also, I would add that Iranians who are dissatisfied with their situation tend to see the solution as emigration. This means that there is not much impetus for radical change at home.
I think the mad mullahs also have developed the economy well. Iran is now surpassing Turkey in standard of living, and likely to go well beyond with the high oil prices, and other resources for that matter.
They have also dramatically expanded industrial production. It blew my mind when I was reading about world automobile production around the world.. out of curiosity. Iran went from producing something like 15,000 cars in 1979 when the mad mullahs came to power, to 550,000 in 2003 I believe was the data I saw.
I'm not sure how other industries are developing but I would bet they are building up too, like I know their arms industry is, and of course the well known nuclear power program. The long story short is imo, when you are creating good jobs, or at least better jobs then the people are used too, and covering social costs with the oil money.. People may complain but they aren't likely to rise up. Also the mad mullahs are smart enough to allow some democracy, and also loosen the strict social conservatism slightly.
I don't expect Iran's population to rise up, unless the economy tanks, or the social conservatives push something that infuriates the population, like banning condoms and birth control pills. I also would be glad to debate with someone who believes revolution is likely in Iran, to learn more about it.