It was recently reported that Battle.net users with Iranian IP addresses were being locked out of Blizzard's Battle.net service, and thus, all of their flagship games: Diablo 3, Starcraft 2, and World of Warcraft. It was speculated that this was due to content the Iranian government found inappropriate, but as it turns out, the line was cut from the outside. As a Blizzard employee has revealed on their official forums , the outage is the result of sanctions imposed by the United States government.
VG24/7 reports that Battle.net isn't legally available in Iran anyway, but that virtual networks have until now allowed citizens to access these games. Presumably these new procedures Blizzard has implemented have cut off this Terms of Service-breaking means of access. Strangely, the VG24/7 article also reports that Blizzard would "happily lift these restrictions as soon as US law allows.” This seems to suggest that Blizzard does not take issue with Iranian gamers accessing their servers through virtual networks to bypass government restrictions.