It is the low cost of Facebook (and social media) messaging that makes me not use it to send messages to people I love and care about. I still call them on the phone. When it comes to relationships, my communication theory is simple: the cost of the medium is the information. Goes without saying in this setting, there's only few people I call "friends."
If you have more than a handful of people that you wish to meaningfully connect with - facebook is a great tool. I know personally many people including myself that both use calls, emails, chat messages - and yes, facebook - all with the same people. They are just geared towards different kinds and modes of communication. The notion that I have to use phone exclusively to communicate with someone to call them "friends" seems very dated to me personally. It probably works for someone else. (But I mean the numbers show that a lot of people do indeed find facebook useful, it is not that popular for no reason.)
It's about the connection itself, it's about the energy and attention one puts into the relationship, not whether one allows oneself to use facebook for it or not.
