It's been suggested that we Brits tend to text each other more than call each other on our phones, and the tone of these suggestions is often that this is to some kind of detriment to our interactions. While I suspect that similar accusations were levelled against phone calls versus face to face conversations once upon a time (and possibly still are) there are some things to consider about this trend.
I've never been particularly comfortable with phone conversations as an extension of my general trouble with personal interaction; the thought of calling someone on the phone for a conversation makes me vaguely and irrationally anxious - but this isn't the reason why I use texts (or iMessage) primarily.
A phone call is immediate, other than the prospect of leaving voicemail, and they'e of a limited duration defined by the circumstances of the participants. These aren't often problems but clearly are not advantageous. Text messaging lacks this limitation. A text message is infinitely patient, will persist beyond the conversation and allows for a conversation to take all the time that it needs. A text conversation can happen slowly over a week, will wait for you to attend that meeting and is forgiving of the fact that participants may be in significantly distant time zones. A text message can also be dramatically more discreet. A phone call is still the option when urgency matters, but often the timeless nature of a text message is simply convenient.
If anything smartphones simply play on this trend, expanding on the methods in which we can exchange information with the gadget in our pocket. Twitter, Facebook and so on share a lot of the same benefits that make text messages so popular. If this means we're eschewing the humble phone call then I'm not convinced that's a great loss - certainly there are gains and benefits of this trend to balance out anything we forego.