"What new things could we discover if social network analysis took time and space into account, in addition to the raw connections between people? In most cases, social network analysis today is limited to discovering friend connections, community leaders and outlines, influential people and personal friend recommendations - in a static or snap-shot kind of way. If new factors could be taken into consideration, specifically changes over time and space, then social network analysis could discover things like emergence or decay of leadership, changes in trust over time, migration and mobility within particular communities online. That's very valuable information that the social web has barely begun to tackle capturing." - from here.
A very interesting read. Time as a factor in the soical graph analysis.