I really don’t think of Quora as blogging. More in the nature of Linkedin Answers or Yahoo! Answers. But Scoble does make a point as to what it borrows from.
I don’t think Quora will replace or even be a substitute for blogging by a long shot. The big value it has is the quality of people who are answering, IMHO.
So, what is the innovation here?
First, it learned from Twitter. Ask your users a question and they’ll answer it.
Second, they learned from Facebook. Build a news feed that brings new items to you.
Third, they learned from the best social networks. You follow people you like. But then they twisted it. You can follow topics. Or you can follow questions in addition to following people. This is great for new users who might not know anyone. They can follow topics.
Fourth, they learned from blogs about how to do great SEO. I’ve started seeing Quora show up on Google.
Fifth, they learned from FriendFeed, Digg, and other systems that let you vote up things. If you watch a question that has a lot of engagement you’ll even see votes roll in live. It’s very addictive.
Sixth, they brought the live “engagement display” that Google Wave had: it shows who is answering a question WHILE they are answering it.
Seventh, it has a great search engine for you to find things you are interested in.
Anyway, I find that there’s something addictive about participating over there instead of here on my blog. Why? Because when you see people voting up your answers or adding their own replies in real time it makes you realize there’s a good group of people reading your stuff. I don’t get that immediate rush here (here I have to wait for comments to show up, which isn’t nearly as immediate).