And since he deems it un-Islamic to own a Facebook page, it's therefore a sin:
"Basically, going to any website which propagates immoralities and could weaken the religious belief is un-Islamic and not allowed, and membership in it is therefore haram (a sin)," the ayatollah replied.
"Only the use of websites propagating religious criteria and not leading to any kind of ethical immoralities is of no problem," he added.
As of October last year, the official estimate of FB users was 17 million, though that figure is probably inaccurate given the fact that many young Iranians have found ways to get around the severe restrictions placed on internet use in that country.
Over 5 million websites are reportedly blocked in Iran, but Iranians use proxy software and virtual private networks (VPN) to access them.
Iranian officials have, for over three decades, been waging what they call a "battle against the invasion of Western culture."
This has led to blockades of "immoral" internet sites and banned Western music and movies. However, pirated versions of those are easily available on the black market.
Where there's a will, as they say.
So, with a population of about 70 million people, approximately 25% or so of Iranians are sinners.