From The Article: "Time Spend by Average Social Networking User per month (Infographic compiled and designed by Go-Gulf.com)
Thus measuring time spent and user engagement reflects poorly on the benefits of Google+ which are really all about one key thing: search.
Search engine optimization for any given site has always been important and it’s becoming even more so with the constant updates being made by Google, Yahoo and Bing, both on the web and the mobile web.
Not to mention the increasing trend where social, local and mobile are morphing into one big platform where reaching and engaging with customers will be the utmost challenge.
Posting on a Google+ brand page helps your rankings, in particular as Google rolls out more changes with regards to travel search, Places, Maps and other integration projects yet unannounced".
Via Antonino Militello