Say that in the near future you will be able to post a question on social network sites. You will get many different answers (whose quality may vary). It would be nice if you could get a list of answers ranked by quality.
Problem: how to rank answers? That’s a cool problem that is disappointingly hard to solve.
Some would argue for using social networks – people close to you should be trusted and they can surely answer any type of question. For me, that’s hard to believe. That is probably because my friends have diverging interests (a few know about technology or finance, a handful of them knows about literature, and many about architecture and design – I have a weakness for creative people). And they also think differently – I’m fortunate enough to have few friends who are left-brainers, while most of them go for the “right” side. If many people would go along with my personal experience, then we could deem those solutions oversimplified at best.
So how to go about the initial problem? For a start, I would acknowlege that:
a) “X befriends Y” and “X trusts Y” are two totally different concepts. I’m overemphasizing by saying “totally”: after all, there may be a correlation between the two concepts; but it is difficult to buy into the causation arrow “I befriend you” -> “I trust you”. Therefore, that distinction may be important (if not crucial), and we usually underemphasize it “for simplicity’s sake”.
b) “X trusts Y” has little meaning. Since trust is context dependent (1, 2, 3), one needs to specify for what X trusts Y. X may trust Y for academic tips but not for real-world issues ;-). So a better way could be “X trusts Y for doing Z”, and that Z would be crucial.
Given these two points, I really like this recent paper. The authors separate social networks and webs of trust (which they call vote-on networks), and they are planning to build around context-specific webs of trust. Great work!