Read a few papers presented at last International Conference on Weblogs and Social Media.
Some interesting findings:
“web-based knowledge market” – monetary award is not a significant incentive for people to participate in a task on a knowledge sharing market.
Competing to Share Expertise: the Taskcn Knowledge Sharing Community – In general, forums in Yahoo answers tend to have broad
out-degree distributions. In the Programming category this represents a few highly active individuals who consistently help others with their tasks and problems, but do not necessarily ask for help themselves. In the Marriage category, these could be users who regularly offer advice, or are there for the fun of discussion, as is the case in the Wrestling category. Note that this separation of roles is evident even when one considers whether a user posted a single question or answer. For instance, in Programming, about 57% of the users who asked questions did not answer any during this time period, and similarly 51% who answered questions did not ask. Overall, YA is very broad but not very deep.
And you can decide whether you can befriend with one or not by looking at his or her Facebook profile in 6 seconds.