Chris has been getting some friend-spam and asks whether Orkut (and other social software) is "purely a networking device (in which case we are all each others friends) or is there supposed to be some relationship present to justify the link?" In other words, he continues, should we consider the quality of the link?
In the real world, of course, there are degrees of friendship. Actually, not only are there degrees, but there are degrees that are often very difficult to define and quantify. Maybe you can't necessarily 'rank your friends', but you can definitely create general buckets of overall relationship quality (even if the criteria is vague and subjective).
Capturing the relative quality of the link is even more important when you start building networks out of the links. My connection to a good friend's good friend should be a lot stronger than my connection to an acquaintance of an acquaintance - even though they are both technically just one friend removed.
Of course, this is a relevant discussion in the security space as well, especially when it comes to authentication and authorization. Most schemes don't have a way to represent how much I trust a domain, site or machine - only that I do or don't trust it.
Personally, I won't consider any social sofware 'successful' until it accurately captures this dynamic.