I just started playing with the new circles which link dna matches and trees and it looks like it only works for people with public trees! That means private tree and no tree people will have an incentive to share information to get these results. (it isn't the leaf thing, but something more interesting combining both)

I have scanned the white paper and it is quite interesting. It found me a person who is in the dna data base but doesn't match me but does match my other matches and we have public trees showing us where the common match is...like the in-common with tool on FTDNA. Very interesting!