tl;dr: Rather than fighting about Privacy or Sharing we should be developing two layers of the web in tandem: a 'Privacy Layer' and a 'Real Person Layer.'
Quora seems to be reproducing the success of Wikipedia but capitalizing on authority by leveraging real people with real names. Instead of an anonymously sourced Wikipedia article, you have answers backed by the authority of a particular persona. This has the advantage of (1) letting people know if they should take this person seriously, (2) this person's answer will now be a matter of public record, so their status and 'street cred' rides on the accuracy of their answers.
It seems that real people and real faces are what make Facebook such a resoundingly popular site. Finally you don't need to guess which of the friends whose phone number or email you do have, might have a way to get in touch with one of your old pals with whom you've been out of touch. You can just friend them on facebook and whenever you need to be in touch with them in the future, you can just poke/message/post them.
All of this makes me wonder what other Web Successes out there will be reinvented as real people with real names. Search comes to mind. Eventually someone will come up with a better search than google, based on the social graph. By better I don't mean algorithmically or even measurably better, but something that feels more helpful to a person trying to find something they need. (I suggest when it is created, that that industry focus on the verb 'Find' rather than 'Search,' which is what a person would rather be doing.)
There's also room for a Real People Amazon, and a Real People EBay. This space could get extremely interesting. Also a formalized Real People Tumblr or other centralized blogging podium.
In some ways it will greatly improve the web experience. The web's inherent anonymity is great, and it definitely isn't going anywhere, but that's what I would call a 'Privacy layer' of the Web. There's another layer where open sharing and known identities can be extremely meaningful in addition to just being useful.
It's at the crossroads between these two layers that everyone is running in to trouble. When Mark Zuckerberg talks about the benefits of sharing he's really talking about the benefits of a 'Real Person' layer on the web. When critics fire back that people should have the right to hide whatever they want, they're talking about the 'Privacy Layer.' I think for the web to be truly useful we'll need to develop both layers.