The feeling of connectedness (and thus, the usefulness) of Social Networks and Ambient Awareness environnements is very hard to explain without actually experiencing it. David Allen did not find a way to actually explain this feeling, but he gives some inspirational clues:

There is inherently some sort of magic between the lines in much of it that seems to have struck a chord in so many of us. I attribute this to the transparency, connectedness, and immediacy that social media offer, which are key attributes of quality relationships—something humans crave at a basic level.

Time Management in the Age of Social Media