Iran wants to prevent users from getting into the Tor network and going to sites that they do not have control over. Since it is easy for them to block the public routers Tor uses "bridges" which are nodes that will allow people to connect to the entry nodes through them. The lists of these nodes are then treated as semi-secret (in that they try to limit any one person or organization from learning all of them). This is exactly what they are looking for people to make, more bridges, not more exits.
edit: They actually say that Iran does very little active blocking and are just throttling anything that looks like TLS, so the bridge vs. entry node distinction does not really apply in this case, but it is relevant to the attack you are trying to describe.
Tor also has a well-established way of fighting blacklists. Normal relays are all listed on a public network, but there is also an opt-in program which exists for Tor relays: a Tor relay can choose to be "hidden" in a certain sense. A "hidden" relay node accepts only entrance connections, and these are advertised more quietly by the Tor Project folks, who don't reveal too many too fast. It is therefore the case that blacklists can be circumvented by asking Tor for a couple of hidden entrance nodes and configuring yourself appropriately.
The goal of obfuscation is to buy a little more time during which people can use encryption again, by making the encryption look like normal traffic. (But I have no further knowledge of the particulars, so take what I have said with a grain of salt.)
why don't you, you know, read the link that this thread is about before commenting?
High Quality H264 link (720x576): http://mirror.fem-net.de/CCC/28C3/mp4-h264-HQ/28c3-4800-en-h... (found on the YouTube page)
If del.icio.us is able to do it[1], surely Iran must be able to too.
[1] https://news.ycombinator.com/item?id=3567996