Don’t know what that is? Well, you know about broadband. Thinband is the deliberate bottlenecking of ASDL connections to consumers and Internet cafes to 128kbps (but not to businesses). Where did this come from?
Why, from none other than Mr. Dinner Jacket:

Internet technicians say speeds of 256 KBps, 512 KBps or higher are increasingly common internationally. Iranian surfers will now find it much slower to download music or anything else from the Web. Businesses have not been affected by the move.
Critics said the restriction would hinder the work of students and researchers but said it appeared in line with what they see as a squeeze on the media by the government of President Mahmoud Ahmadinejad, who rails against the West.

In other words, the Mullahs don’t want a revolution on their hands. I’ve got a great analogy from BSG: the Cylons limiting the artificial intelligence of their “bullethead” Centurions...not giving them sentience, preventing them from rebelling, like they themselves did 50 years ago against their human masters.
The techs inside Iran...as well as those outside Iran who are against the Mullahs...will eventually find a way around the Thinband restrictions. The one thing all totalitarian regimes have in common is that they want to keep the masses dumb and uninformed; information kills them. So there is still time.