In episode 199 of Semantic Mastery's weekly Hump Day Hangouts, one participant asked how to determine whether a social website is good enough to be included in a network ring.
The exact question was:-
How do you determine if a social website is good to have in a network(ring) or not? There are over 200 popular social websites in the world (I looked up at google for some articles about social networks lists).
I would have thought that StumbleUpon will be a good social website to include but you seem to neglect it. How one can determine by himself if some social website is good or not, besides asking you for each and every one that exists and comes along.