I'm not so sure. Privacy is a big deal for me, but I'd sign up to something like this. If:

If it uses a mechanism like CardSpace (http://en.wikipedia.org/wiki/Windows_CardSpace) had:

=> I own my own data (client-side encryption on my client)

=> I consent to others accessing my reputation. Note that access means others can see, not get a copy of, and not keep.

=> I can withhold my reputation completely, or delete it at will.

In such a world, as Airbnb for example, I might make it easier for someone willing to share their reputation to rent a room. A non-existing or withheld reputation might require other checks (like a credit check), or verifiable references, for instance.

If thought through this might have uses. Primarily I'd need to know that it abides by the 7 laws of identity (http://technet.microsoft.com/en-us/magazine/2006.07.7laws.as...). A lot of this technology exists. CardSpace is one example of a client app (I wouldn't use a web app to manage my reputation, but would be ok to use a service to let others leave feedback about me). Attribute provisioning in identity federation is another, and could be used as a mechanism to check someone's reputation, or to give feedback.

Something like this COULD work if done well. at the same time,it is also hard for one to protect oneself against identity thieft.But I guess this kind of public only social network could also be used by third party websites as an OAUTH provider. I post as little as possible on the web about myself in fear that others would use my identity for a scam.So if someone can fix that problem,it could be a killer product.