Doesn't watching and liking a video add another + and some other stats to your google+ profile?
Problem with it is google tied it into all of their services, and they all interact with eachother, so its really hard to tell who really uses it.
So does using facebook to authenticate on other sites or games (lots of which are available for mobile devices), clicking "like" buttons or using the facebook chat (even if on a third party client). All that counts as "social activity".
I don't know a single person that uses g+.
There isn't as much people I know in real life using Google+ as in Facebook (although there are quite a few), but on the other I find much easier to communicate with people you don't actually know but that share common interests on Google+ than on Facebook.
Just take a look at the Communities in Google+ and you'll find people talking about pretty much any subject you might be interested in... that is, Google+ is actually more similar to Twitter than to Facebook.