WSJ, TechCrunch). Maybe this has something to do with Google turning on HTTPS as a default setting for all Gmail users (and making it harder for snoopers to find out what's in the emails users are sending). That was in response to Chinese hackers (government backed?) snooping on Chinese activists using Gmail. Everyone using secure communication makes it harder for for snoopers to find the needle in the haystack.
The ban on Gmail will probably be as successful as the ban on Flickr, Twitter and the bans on Facebook. Iranian Gmail users can take heart in knowing the Iranian government will be launching its own email service. I'm sure the web-based service will have all the same innovative interface features that have made Gmail so successful such as threaded conversations, keyboard shortcuts and sophisticated filters. I doubt they'll be data-mining the content of emails for targeted adverts, either.
Iranians who do decide to use the government's email service can take some simple steps to ensure secure communications over an insecure service. Tools like FireGPG help you encrypt the content of your communications. Details on how to use it here. It needs a smart Iranian Firefox user to integrate it, in Persian/Farsi, with the email service.
If secure communication channels are criminalised, only criminals will use secure communication channels.