Reciprocal vs. passive models of friend-building in YASNSes

A few days ago,Jen Golbeck, a Ph.D. student in computer science sent this message to her friends of friends at Orkut:

Christian > Dan > Jen 3/9/2004
from: Jen
to: friends of friends
subject: Social Nets: Obligated to add friends?
message: Hi,
It seems to me that a lot of friend connections here are made because we feel obligated to reciprocate when someone adds us to their list. I want to make this claim in a paper, but I need some evidence. If you have a second, I have a form that just asks how many friends you have on orkut and how many of them are on your list only because you felt obligated to add them.
I appreciate the help.

The same day, Clay Shirky contrasted two (or more) friendship-handshaking models by discussing recent changes at Friendster and Orkut in YASNSes get detailed . He notes that the more fine-grained, pseudo-nuanced gradations of friendship require a lot of maintenance work and seem to only give value to the owner of the network, and also that passively ignoring friendship requests models real life more accurately than a challenge-accept/deny model.
He also points to LiveJournal as a good model and claims that “Those who do not understand LiveJournal are doomed to repeat it, badly.”
The discussion that follows is spirited, with Stewart Butterfield of Ludicorp (the Flickr people) challenging many of Clay’s conclusions.
BTW: The Orkut message in the previous post told me it was coming from “clay.” At first I wondered why Shirky was sending out a press-release for Blue Digital.