I discovered this with the profiling tool in xcode for v1076 and checked to see whether it existed in the latest beta (B11). It looks like it does.
This occurs on the default program for the mac_template from beta 11, I haven't adjusted or added any code at all. I simply linked up the headers and libraries and then began profiling.
I haven't yet tried on any other platforms but it looks like something specific to iOS/Mac (I'm still tackling the fbSDK on iOS)as it points out NSMutableArray.
The good news is that it's not a large amount, only 32 bytes.