They say that when the costs–the time and effort–associated with being a member of a social network outweigh the benefits, then the conditions are ripe for a general exodus.
So in this digital autopsy, the cause of death was a drop in the cost-to-benefit ratio. “This measure can be seen as a precursor of the later collapse of the community,” they conclude. But a contributing factor was also the k-core distribution.
Who'd a thunk it.