Are all members of my social network(s) equal?

I was thinking about Charlene Li's blog about social networks (Yes, again) and one paragraph stuck in my mind where Charlene talks about the possible uses of my social network in shopping environments.

Instead, I want to see reviews from my friends when I’m in the book buying process – on sites like Amazon.com and BN.com. It would mean a lot more for you to look at the Groundswell page on Amazon, and because you’re sign-in with your email address, be able to see any review a friend has written about the book – even if it’s on their personal blogs. That’s the epitome of social networks being like air, when it’s integrated into everything that you do.

I like the idea of the social network being relevant in a particular context (I've blogged about this in corporate settings). If I'm shopping for books, I want to see the book reviews of people in my network. Of course, the problem comes about when I have a huge social network such as that of twitter where I may have thousand of friends. If I have to dig through all those reviews, I'd go crazy. Not only do I have different social networks (perhaps this is just a current restriction of the plethora of social network sites which are available and which don't often share members amongst themselves), I also have different relationships with members of these networks. Some might be personal friends, some might be co-workers, etc.

Furthermore, I may have some personal understanding of the qualities of the members of my social networks. For example, some members share my tastes in music, others have similar interests in books. My impressions of these individuals may also be different from other members of their social networks. I don't know whether these are "sub-networks" of my existing networks ("Facebook friends who have similar interest in Chinese cooking") or new networks. The thought that such networks could exist in the social network cloud (members from LinkedIn combined with Facebook and twitter) is also interesting. Of course, a meta-social network is difficult in that there are many niche social network sites whose collected data reflects their specific interest area (A site focusing at soccer-related networks probably will not acquire information about which books members have read).

Returning to Charlene's example of interaction of social networks in the shopping context, I think that it would much more appropriate to get advice from the select few who taste in books are similar to mine rather than the book reviews of all those individuals in my social network (although this could be provided if desired).