There are many many flaws. It won't work, and they only reason they are trying to make it work is because it is the *only* possible long term sustainable revenue generation mechanism for them, and they know it.
But, as you say, it is logically broken. Further to it being broken, they risk destroying the function of the entire place that encourage people to go there ATM if it becomes some sort of recommendation/yelp market where pressure to share everything you buy, eat, listen to and watch takes over. Indeed ironically enough, google+ is actually a better platform for this to remotely work, as there is more of a culture of people grouping around topics they like rather than seeing the place as a real-life friend noticeboard/inbox.
But we can observe from the sidelines as fb try and fail. Watching the media fawn over MZ is much like watching how they fawned over people like Lance Armstrong 5+ years ago - for those who have a decent amount of knowledge it is clear that there are fraudsters at work - but the media are not interested in destroying the story. By keeping it alive they can file page after page of copy.