I've noticed that both Facebook and Twitter have absolutely increased my 'dunbar' number - I am now in touch with many more people because these tools make it easy. The value is not instant though. I've found twitter useful only after twittering (or is it tweeting?) for a few months.
Agreed. My number dunbar number has increased as well. The concept of ambient awareness is interesting as well. The other day I had an out of state, non-Twitter using family member ask me about something that another out of state, Twitter using family member had mentioned she saw me post on Twitter. It was a strange moment having it come back to me like that, but in that moment I realized how powerful Twitter can be.