(Posted as an answer due to the length.)
Quora is just starting up. They want to be a definitive source for everything that is asked on it. It might not be easy, but surely achievable. They plan to make it available for scraping, and their terms are slightly open. They might make it big, and we will have another resource to link to (like Wikipedia) and that is not bad, but will they share the same ethics? In the future, we may see Stack Overflow providing quick answers to the questions at hand and linking to Quora for further intensive reading on the topic at hand. The intensive nature of the content, IMHO, will define the crowd at Quora, which will be different from Stack Overflow (but will have an overlap nonetheless).
Send questions to experts on any topic
That is not what Stack Overflow does, we allow "experts" to see the questions, but we do not "send" questons to other users or experts. Such questions Quora would probably be tweeting or pasting to the walls.
Answer questions by following topics
that interest you
This is what Stack Overflow does.
Build consensus around the best answer
The same as with Stack Overflow, and even the screenshot is so similar.
Quora Usage Terms vs SO License
Subject to these Terms, Quora gives
you a worldwide, royalty-free,
non-assignable and non-exclusive
license to re-post any of the Content
on Quora anywhere on the rest of the
web provided that the Content was
added to the Service after April 22,
2010, and provided that the user who
created the content has not explicitly
marked the content as not for
reproduction, and provided that you:
(a) do not modify the Content; (b)
attribute Quora with a human and
machine-followable link (an A tag)
linking back to the page displaying
the original source of the content on
quora.com (c) upon request, either by
Quora or a user, remove the user's
name from Content which the user has
subsequently made anonymous; (d) upon
request, either by Quora or by a user
who contributed to the Content, make a
reasonable effort to update a
particular piece of Content to the
latest version on quora.com; and (e)
upon request, either by Quora or by a
user who contributed to the Content,
make a reasonable attempt to delete
Content that has been deleted on
Terms which do not match:
do not modify the Content is starkly against CC-by-SA's
You are free to Remix
upon request, either by Quora or by a user who contributed to the Content, make a reasonable effort to update a particular piece of Content to the latest version on quora.com has no match in the CC-by-SA license.
upon request, either by Quora or by a user who contributed to the Content, make a reasonable attempt to delete Content that has been deleted on quora.com has no match in the CC-by-SA license.
Terms which match:
attribute Quora with a human and machine-followable link is similar to
You must attribute the work in the manner specified by the author or licensor
upon request, either by Quora or a user, remove the user's
name from Content which the user has subsequently made anonymous vs CC-by-SA's Moral Rights Clause
In addition to the right of licensors to request removal of their name from the work when used in a derivative or collective they don't like, copyright laws in most jurisdictions around the world (with the notable exception of the US except in very limited circumstances) grant creators "moral rights" which may provide some redress if a derivative work represents a "derogatory treatment" of the licensor's work. appears deceptively similar to me. It may also be compared to the Privacy part of the CC-by-SA license
Quora's license terms are not so open at the moment, especially due to the absence of remixing rights. This is surely not something that Stack Overflow would like to emulate.
Avid (and) users of quora (I don't have an invite), may be able to tell more.
If they want their question page to be THE authoritative page for that topic, they are aiming towards being an encyclopedia, rather than a question and answer site. Authoritative content which already exist in textbooks, may not always be reproducible in full without trampling on copyrights. And content produced by "experts" may not be authoritative for everyone.
Stack Overflow's philosophy of making the Internet a better place is more valuable than making a website "THE" place for something.
As far as Quora's social links are concerned, using Facebook to recruit users is something that some of Stack Overflow's sister sites try (but on a different and smaller plane). If Quora can attract Facebook's crowd to use Quora for their discussions on sundry topics, we will be looking at massive ad revenues for Quora, but with a lot of noise on their authoritative question and answer boards. Geeks (and experts of all kinds) will still flock to the place if the place becomes interesting enough (based on usability and content), and Quora will have a lot of authoritative content. If ad revenues are their primary aim, they will always have to contend with noise, and in which case the geeks will always be looking for a better place.
You need ad revenues, and you need to balance that with your ambitions of what you want to be. It's a tight rope, but I have no idea how that works.