My Google+ network doesn't have much activity relative to Twitter/FB but I still visit it once a day because the content is mostly unique, not the same ones I see on my Facebook and Twitter streams.

For me, G+ is where I post things I find interesting, usually links and thoughts to a relatively limited audience of real-life friends and acquaintances, and sometimes tech-related thoughts to my Hackers circle.

At this point I only use FB for a) chatting with people whose phone number / email address I don't have, and b) to keep in touch with and get updates from more distant family/friends (e.g. "that waitress I worked with a few years ago got engaged-- best wishes!", "it's my buddy's college roommate's birthday-- let's go get a beer in Portland sometime this summer!")

And I only use Twitter to read jokes from wannabe comedians and publicly bitch about corporations...

Basically, I don't want to get a link from the author to her own post, I'd rather get a link from someone who read her post or article and found it interesting. I realize it doesn't involve a sexy machine learning algorithm, but it sure does work well for me.

The twitter-clones tried this approach, encouraging content-"seeding" with a full r/w API. What actually happened is that they (nearly?) all ended up as networks full of bots spamming each other with duplicate content.

And it's hard to sell advertising when your only users are robots.

So whether it took Facebook an hour, a decade or 2.5 years to roll out their API, right now they've got one and right now google is trying to compete with Facebook through their g+ offering.

That must be why ads for G+ are never ever about sharing little silly things with your friends... no wait, they're actually trying their hardest. It's just adoption sucks, so people rationalize it. That's how I see it, anyway.