I can see this being very useful for folks who are transitioning from a college lifestyle into a professional mindset. Until recently, Facebook was at best negligent about privacy settings, though in my mind they've recently (past 1-2 years) tightened up to a point now where it's easy to filter who sees what. Like NomieRae I've got my professional contacts grouped so they see none of my posts, photos, tagged anything, etc... Further, nothing appears on my timeline until I approve it. I've taken the stance the past few years that I won't post anything on social media I won't say to a room of 10,000 people.
It's funny, Google+ is exactly what I need in a social network, but nobody else uses it!