Sébastien Paquet's concept of "community straddling" from " Online Communities and the Future of Culture."
These people do not feel irrevocably bound to a particular community. They see themselves as multidimensional: as opposed to saying "I'm a doctor, don't expect me to teach you anything" or "I'm just a programmer, don't bug me with politics", they'll say "Well, right now I'm into this and that and that, and if you have something new to show me I just might take a plunge!"
"Community straddlers keep the air fresh in a community; they help keep it alive. They contribute to the exchange of ideas between cultures which would otherwise hear little about each other."
The community straddlers are the 'connectors' of social networks and quite possbily the hubs of innovation and value-creation.