The Washington Post writes:
Facebook, MySpace and other Web sites have unleashed a potent new phenomenon of social networking in cyberspace. But at the same time, a growing body of evidence is suggesting that traditional social networks play a surprisingly powerful and underrecognized role in influencing how people behave.
The study apparently show that smokers very often quit in groups in response to changing social pressures in a kind of wave or chain reaction. At the same time, die-hard smokers can become quite isolated.