I run http://www.photoblog.com and at one point a few years ago we were like in Iran's top 100 sites. It was to the point where 25% of our traffic was from Iran. Then that student revolution hit and we are now blocked.
Most blogspot bogs are not blocked in Iran. All of them are blocked. And wordpress blogs, too. Facebook, youtube, twitter, BBC, CNN, tinyurl, goo.gl, megaupload and thepiratebay are a few more examples. Moreover, having a satellite dish is against the law, just look at the pictures in this Persian website:
http://www.asriran.com/fa/news/176720/%D8%AC%D9%85%D8%B9-%D8...
But, in my opinion, these aren't the main problem. The main problem is internet bandwidth limit for home users, i.e. 128 KBit/s. Yeah, that's right: 128 KBit/s.
I have a server in the US and bypassing their filtering system is not a problem for most Iranians but how could you watch a video in youtube with a 128 Kbit/s connection?
I used to have a proxy business; my best clients were Iranian people; a lot of them doctors, PhDs etc who wanted to to hire servers to read / mirror 'Western' information via VPNs. One guy who became a good friend actually ended up buying a rack full of servers via me to provide open communication for all his friends and family.