These countries, Iran and China probably knew that Facebook is a huge spying machine and kept their citizens safe.
1. By blocking big internet companies in the USA it gives homegrown companies an opportunity to rise to spur economic growth and create jobs.
2. Having homegrown solutions that compete directly with US companies is good for the Chinese morale and public image of the government. Showing that they too are capable of creating and running large internet companies that will drive economic growth in the next century.
3. In case of emergency China entities are a lot easier to control the outflow of information. Whereas I feel getting FB or Google to block something might be more of a nuisance. However, while this is the most popular reason why the government has blocked FB and Google (it's fun to vilify governments in general), I believe that in case of emergency they would just shut these sites down, so I believe explanations 1 and 2 are ultimately the bigger impact in this decision.
More like, they didn't want any competition with the government. </snark>
Can you name 1 that has as influence in your life as Twitter, Facebook, Google or Apple?
Why? Maybe its because USA/Western people dont have trust in companies from Brazil, Russia China?
Its not because they dont exist, Orkut was ahead of its time, vkontakte has all that facebook has and pirated music on top of it, maybe its just that you are steered into USA controlled "content" just like Iran, Chinese citizens are steered towards baidu or whatever.