The Friends’ Friends page is an interesting way to waste time reading posts from random people you probably don’t know. (The link here is for my friends’ friends, but you can substitute your own name I think. Might work for paid members and not others, I’m not sure.
The problem with this feature is that if you have any communities at all in your friends list, those community members show up as “your friends’ friends”. Bah, this is next to useless, because I have bookmarked groups with huge numbers of users like paidmembers, polyamory, etc. Even if I wanted to temporarily remove those communities from my friends list and enjoy the friendsfriends for a while, now I’m stuck reading community entries (because my friends have bookmarked those communities as well). I don’t think the filter feature works with friendsfriends at all.
So I have come to the conclusion that the best way to see if your friends have any interesting friends is to go look at their friends pages individually.