Via the Toronto Star (registration required) a discussion of the encroachment of private spaces on public spaces and the way social networks are changing:

"The big change has been this shift from groups to networks," he says. "They're less formally structured, they're more amorphous."
Those in anyone's network don't have to be physically close, just a cell call away, and it's easier to opt in or opt out of a network than it is a group.
"People can switch around and manoeuvre around. What that does is leave them with some uncertainty in their lives but it also leaves them with some autonomy. It's a switch from public sociability to private sociability."
Your cellphone network becomes, in a sense, an extension of yourself, what some sociologists have begun calling "a third skin."
"The notion is that you should be connected at all times," says Wellman.

...via Smart Mobs