I use the "Iconograms" service of the Greek Orthodox Archdiocese extensively, particularly to remind the parishioners of weekday Festivals, such as Epiphany and the Ascension. About 1/3 of those receiving the Iconograms actually view them, according to the read receipts I receive.
The viewing may be higher than 1/3; you can read the email and still suppress the response. I do this sometimes because it implies "Did you hear me, are you listening?"
We do not have Facebook presence, and, if I have anything to say about it we never will; that is, unless FB morphs into something other than the condependency of narcissists who post what they are having for dinner and voyeurs who seek TMI (too much information) about their "friends". At this juncture FB seems to be an Eighth-Commandment-free zone and hardly appropriate for a Christian congregation.
Don't let the silly part of Facebook keep you from evangelizing. It can be very helpful and produce an excellent educational media. Check out "Eastern Prolife" on facebook. (Warning, you have to register; check it out with someone is is already registered.