ItsNotWhatYouKNow.com (INWYK) is YASNS (Yet Another Social Networking Service), touting some of the same premise of social reliability that LinkedIn uses -- "All network contacts are generated through close friends or personal contacts, so there will never be the worry of wondering about random, unknown people."

The unusual features seem to be

• the ability to broadcast "requests from users seeking help, member-to-member discounts or coupons, passing along sales leads, or simply recommendations and reviews." (It's not clear if the broadcast is global, or just across more degrees of separation (which INWYK calls tiers) than your personal network is.
• The ability to have a deep private bio page and a smaller, more public "blurb" (the idea being that share your plushie fetish only wiht close friends, but you want to advertise your catering business to the world.)
• Participation karma, on a point system. Interestingly, points are a purely social metric, and exist only to rank people by participation.
• Last but not least, the involvement of cash money -- 3 bucks a month, on the idea that paying users will stay active and v-v.

We're clearly in the middle of one of those "Everyone decides X is a good idea all at once" booms. It'll be interesting to see how many we get in the next 6 months, and which of them are still around in a year.