Please don't make the same mistake that +Jeff Bercovici
did. Here's a bit from the follow-up to his original piece on Forbes.com http://goo.gl/jihcS
My statement then holds even more true now. I have to work to keep my circles trimmed to 4,500 but I could not possibly keep-up with all the awesome posts that come through my stream. And engagement? There's no way to measure what people are doing.. with the beauty of circle privacy. I'd guess that 20-25% of all my posts or interaction is not shared public.
If you want to measure Google+ vs the rest, look at the last 50-100 posts that come through your stream or newsfeeds on G+, Facebook and Twitter. I'm sure you'll find the most creative, artistic, intellectual or affluent on G+. Now, look at the consideration of the interaction of the last 50-100 posts... which source would you most like influencing your purchasing decisions, business decisions or healthcare decisions?
As for whether G+ should be or will be as big as Facebook? If you look at my bio.. you'll see that I have seen it all
develop online.. being named by Boardwatch Magazine as one of the first 100 people in the world to make a living online. My money says G+ will be the first platform to continue to grow for 10 years, that Facebook has 'jumped the shark' and violated the trust of too many people to regain true trust. The vast majority of people I see say "I still have Facebook because my family and friends are there." They're not GOING there because they get a warm fuzzy feeling from Facebook, they're going there as a means of what they perceive last resort to communicate. I quit Facebook in July...my true friends and family have had no problem emailing or calling me. Hundreds have come here and use G+ regularly as well.
Now that I'm getting close to a TL;DR post... I hope it's not too late to help with your piece.