I'd be interested to see what they define as "daily engagement," for it's a fairly ambiguous term. Clicking on a personalized result in Google search is far different than actively going to the G+ home page and engaging in a conversation. Likewise, starting a hangout is far different than merely +1-ing a foreign page on the internet.
Although all of these actions interact with G+, only few are true metrics of social network success. The key is to drive _social_ interaction, to be the #1 resource of where you friends and family interact. I think G+ still has a wall to climb in that sense.
Similar questions should be raised regarding all other companies boasting their engagement rates. Hit a site with Facebook widhets and comments? Do they consider that engagement? shrug
Although all of these actions interact with G+, only few are true metrics of social network success. The key is to drive _social_ interaction, to be the #1 resource of where you friends and family interact. I think G+ still has a wall to climb in that sense.
Let's not forget their average visit length:
http://gigaom2.files.wordpress.com/2012/01/6a00d83451b36c69e...
I have a lot of hope for G+ but this reminds me of the premature "Mission Accomplished" banner.