Benjamin Waber's research at MIT into social networks has suggested some differences into how people interact and work online and in real life.
"[His] research has evolved into a new field called reality mining. By
tracking people using location-aware devices like mobile phones or
electronic badges, scientists are revolutionizing our understanding of
how social networks function.
Of course, we think we know how they work. We've all become
addicted to some combination of email and LinkedIn and Facebook and
blogs, and at the click of a button we can pinpoint our online friends,
right? But once you step away from your computer, Waber and other
reality miners have found, the real world often works in ways that are
quite different from the virtual one.
On the Web, the best way to solve a problem is to engage an
extensive network; the person who provides information, advice, or
answers is often someone you know only vaguely — a weak link.
In the face-to-face world, though, Waber says, groups are more
productive when the team members know each other well, sharing
extremely strong links. That's because face-to-face teamwork requires
intimacy, he says, and "when you're among friends you can really
capitalize on preexisting protocols" — nods, grunts, in-jokes — for
talking and listening."
But isn't the conventional wisdom that it is easier to find a job through acquaintances than close friends because your close friends all know about the same things but acquaintances are involved in different circles? (Weber comic from his website)
The 
