The tie in was flakier in the past, and at some points in time was done in a strong-arming way, which killed a lot of goodwill (YouTube unification, real name p

The tie in was flakier in the past, and at some points in time was done in a strong-arming way, which killed a lot of goodwill (YouTube unification, real name policy -- enforced from day 1 much more vigorously than Facebook and applying to old gmail accounts, ...) and there was not enough to start with anyway). Couple that with the Buzz fiasco before it .... But that would not have mattered if FB wasn't there. The real problem is network effect: Most people were already on Facebook, and maintaining two presences (FB and G+) was a chore. So most people kept to FB. Everyone I know kept their main profile on FB, and had a "professional" or "interest-based" profile on G+, which naturally saw about 10% or less activity.