I disagree with some of the points in this post. I like Google's hangout feature it is neat for group video chats. I use G+ more to follow than friends. I don't think G+ can beat Facebook on friends feed, however it can beat Twitter for following famous people/tech-writers. Personally, combining the two in Facebook's subscribe feature is a nightmare for anyone having more than 100 friends. Ultimately, G+ will get a niche as Social for their products, but not beat Facebook.
High switching cost for users from facebook to google+. Facebook got strong ecosystem builtup. If there was no facebook then it'd have been different story.
Definitely agree with #1 but teenagers still do video chat so hangouts could take off.