In a nutshell yes. But it's so much better and realtime. You just have to get involved in it to see why it can be quite addicting.

Here's a simple hash:

LinkedIn => Recruiters Facebook => People you don't want to be friends with; Twitter => People you wish were your friends; Quora => Basically Hacker News comments' like quality + twitter like asymmetrical following + domain experts whom you can contact directly! Also, there your upvotes are visible too :-)

Here's a thread on Quora similar to your question - http://www.quora.com/Is-Quora-a-glorified-forum?q=is+quora+a...