I think social networking software has great potential, especially for connecting networks of nonprofits. Personally I have used linkedin extensively, but friendster much less so. I find that for business connections, it is much easier to say "I am a colleague" of someone, versus saying "I am your friend".
Danah Boyd wrote a very interesting piece on this a few years back called "Autistic Social Software" - you can read it here: http://www.danah.org/papers/Supernova2004.html
a relevant quote:
"What does this mean for sociable media? We do not understand how social life really works. Thus, we make crude approximations for it and we make crude approximations for human psychology too. In the tech world, we often make these assumptions based on material like science fiction and pop psychology because we pride ourselves from being removed from an understanding of social life. Simplistic or mechanical understandings of social life are exactly what emerges from autism. From an autistic perspective, social life can and must be programmatically and algorithmically processed and understood on simplistic categorizable levels. The nuanced relationships that people regularly manage in everyday life are boiled down to segmented possibilities. When we teach autistic children to engage in social life, we teach them things like facial expressions. We tell them that a smile means goodness; that a frown should be concerning. Step by step, we dissect social affect and try to formalize it so that these kids can understand the world. This is also what we do with computers. How different is this from asking "Are you my friend, yes or no?""
LinkedIn is also great for finding contacts at companies you are interested in working with, and really shows off the "Strength of Weak Ties"
Sometimes, the people you know the least end up having the most useful connections. What is great about linkedin is it lets you mine this information, without bothering your friends and colleagues with emails and address book searches every time you'd like to find someone working at X.
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