Well, mutual friending isn't guarantee of a relationship, either. I have plenty of people who've friended me and never commented even once, etc. I still include them on flocked post, unless I'm filtering to a smaller group.

With DW I really do try to friend everyone, but some I just can't. There's one person whose DW is only their twitter posts and while I'm willing to scroll past those for someone I'm friends with or who has other interesting content, I'm really not for someone who never comments on my posts and has no other content.