I wouldn't worry too much about Facebook or Twitter or any off the myriad of other instant messaging and social network web sites past and present. They are mainly for young people who don't have really nothing much to say as you have described (there are off course the unusual exceptions), in fact the process of describing how to use the communication tool becomes a totally dull point of conversation for the young folks even in trendy bars
. For those who remember AOL IM, Yahoo messaging and even Myspace etc and the all the other now instantly forgettable interweb social media website, folks will soon get tired of the novelty. I remember using instant messaging on an BBC microcomputer Econet (early 80s) years before the invention of Internet World Wide Web, and it held my interest for about 15 minutes.
I still have trouble responding to folks at work who insist on using Microsoft Office Instant Messenger when they are at a desk 20 feet away.
Facebook, Twitter etc is in reality an anti social web site as it creates a tunnel visioned, blinkered view of what is really going on in the world. Just look at Youtube Justin Beiber viewing stats.
We didn't have a problem in the 70s and 80s, when we had 3 TV channels, a few radio channels and half the population didn't even have a POTS telephone in the UK. There was a lot less hysteria, panic, fear mongering and general unease generated by the media and state back then (and we had 1000s of nukes pointed at each other during the cold war).
I think I've got around 3000 unread emails in my inbox at work at the moment.
http://www.itelegram.com/ might be a better tool to ensure your emergency message gets through.