Mathemagenic

Bill Ives puts it nicely:

From an individual perspective blogs offer:

Creation – publishing content within a personal voice
Collection – managing personal content in a searchable archive
Context – applying commentary to content you manage

From a networking perspective blogs provide:

Connection – discovering others with your interests
Conversation – engaging in dialogs on an organizational or global basis
Community – building networks around shared themes
Collaboration – finding new business partners

I'd add a big picture (corporate or community perspective): aggregation, emergence of unexpected, tapping into invisible...