The US asked Blizzard (delivering World of Warcraft) to block Iranian customers/users/players. On a purely economic rationale of those types of sanctions, it makes sense: the US company conducts business with Iranians: that business is about providing them with a service, that of playing a game, like they would if they were sending a tangible version (say like Monopoly, for the sake of the argument). In that sense, the link with the freedom of internet is quite tenuous.
however, the logic would extend the ban to any US companies with a presence on the web, i.e. at a guess at least 60% of them. Google, Yahoo etc… should stop appearing on Iranian screens. Hum, not sure it is the best approach then… or is it? Given the predominance of US companies linked with the internet, if their Government bans their interaction with countries it black-listed, what happen to the medium of communication that is internet? To take an analogy: the telephone. Imagine that the telephone worldwide is predominantly courtesy of the US companies; banning trade would mean no telephone for Iran. So what would happen? Iran setting up its own telephone that allows contact with the US? I know, in a way, for the telephone, it is exactly what happened; many countries have their own telephone companies. And China does it for the internet: it even created its Baidu search engine to compensate for having blocked google.