Iran has had it up to here with the Internet—Google's easy access to information, iTunes' funneling in of Western Media, and don't even get them started on Stuxnet—all totally the Internet's fault. So, to preserve theocratic rule in the modern era, Iran is cutting off the Internet. Like, completely.
Iran has already taken steps to filter filth from reaching its citizens. Iranian leaders cut off VPN access before recent elections (who needs the BBC when you have state-run media?) and are currently working on their own "Clean Internet," which should be functional by August.