Surprisingly, you can get to know those random friend of a friend folks fairly quickly.
That is after all one of the ways we make friends in real life.
I have a FaceBook account that links to my real friends and I have a FaceBook sock puppet I created specifically for gaming. One of the games let me locate the user profiles of people I was attacking. After I finished beating the snot out of them, and occasionally getting the snot beat out of me, I would offer to friend them to compensate them for the damage I just did (or to avoid inadvertently attacking the people who beat the snot out of me). I'd say 95% of the people to whom I sent the request friended the sock puppet without a second thought. One guy from Israel did run me through the ringer with questions before friending me. At this point I would count 75% of them as acquaintance level friends - people you know and would say hello to at the bus or train stop, chat about the spouse and kids, what they are doing this weekend even if you wouldn't count them as a friend friend if you get what I mean.
But yeah, I am concerned about this new all encompassing interface, even if I don't opt in to it (which assumes it will BE opt in, a huge question in and of itself given Zuckerberg's previous forays into "security"). It might be enough to make me kill the accounts and tell my mother to do the same. I'll wait a bit and see, but it is starting to feel more dangerous. And that's more of a problem for Zuckerberg than Google will ever be, even if he is too stupid to know it.