Phone is the most effective social networking mechanism invented by man kind. Second to in-person interaction, of course.
The social networking businesses have not yet been in the position to incorporate that amount of effectiveness in social communication platforms built by the likes of Facebook or Twitter.
I like both of them (although don't know what utility I draw out of either of them) but I still cherished the opportunity that I had to build an effective solution out of the VoIP capabilities. Albeit, I was trying to do this a few years ago and software capability and communicative modes has really evolved in the last three years. I also had the handicap of not being in control of my own destiny then.
Postings like the following "Phone Numbers Are Dead, They Just Don’t Know It Yet"/ make me laugh and wonder whether we have really evolved technically in the right direction. Predictions of phone disappearing is an urban myth. However, I do see that the reachability and connectivity is becoming more and more pervasive. Capability of talking would appear on devices that we don't consider today.
My iPad, iPhone, laptop, wrist-watch, etc will all be enabled and more importantly all of them would know how and when I can be reached. That is the most effective point hear that many may not get yet.