This is taken from these notes on a talk Joshua Schacter gave.

As the population gets larger, the bias drifts; del.icio.us/popular becomes
less interesting to the original community members. Work out ways to let the
system fragment in to different areas of attention.

The common cause of a group shifts; in a system like delicious the center is statistical. In other groups it’s a more social construction. Effected by cliques and leaders. Then of course there are the shifts that come from the group’s relationship with it’s surround.

It’s a very nice talk full of things which are true, except when their not.