"If I go to a viral video, and I see comments on it from people I actually KNOW, I personally think that would be really cool. That was completely impossible, the old way."
I keep seeing companies pushing this idea on us, but I just don't get it. The math doesn't work. There are umpty millions of pieces of "content" that might be reviewed. I have at most a few hundred actual friends. (I imagine those who push beyond that have also pushed well beyond the intimacy frontier where they really care what you think about YouTube Video #283572738.) The median number of reviews that a given friend is likely to generate in a sufficiently formal manner that Google can figure it out is zero.
If you live in some sort of bizarre homogenous bubble where all your friends are just like you and have effectively the same tastes, and a lot of your friends insist on reviewing every last Youtube video they see, and yet, have some sort of diversity of opinion that you might actually care about, this might work.
But even stereotypical college students don't live like this. Maybe frat houses, but even then, you've got family circles, other non-frat friends, etc, and I doubt your frat brothers are going to be sitting there churning out enough reviews on things that you all care about that seeing a review from someone you "know" is going to be anything other than an exceptional occurrence, and a review you care about even less so. ("Yes, my frat brothers love the latest Call of Duty. I could tell that by the way we all played it for 14 hours straight last night. I did not need Google+ to tell me that.")
(If they did sit there and review everything, it would just turn into a backchannel for chat anyhow... "This beer is awesome, just ask John about last night... here's a link to some photos that the beer company would pay good money not to have associated with their beer...")
I'm not saying that there's absolutely nobody this will be useful for, but it seems to be a very, very specialized group of people hardly worth the immense effort being put into this idea by companies. The amount of possible "things to review" just swamps the number of friends a person can have, and standard lurker/poster ratios tend to imply that "nobody" writes reviews. (And I gotta think these sites have even worse lurker/poster ratios than something like Usenet or HN, probably by an order of magnitude or two or three.)