Comment No need to overthink this (Score 5, Insightful) 359
Google's social networking features remain marginal for the same reason all of the other social networking sites remain marginal: the value of a social networking application is proportional to the number of people who are already using it. And Facebook hit critical mass first, which means that anyone who wants to "socialize" online with all of their buddies is going to want to do that on Facebook, because that's where all of their buddies are to be found online.
Asking people to also sign up for a second social-networking service is a losing proposition, because it inconveniences them (now they have to check two sites every day) without providing any compensating benefit (why talk to their friends on site B when they could already do that on site A?).