I just read a forwarded article from Singapore newspaper The Straits Times, this unknown writer name twitter a social networking website.
Twitter is not a social networking website, at lease for me.
I met many people who just thought that community website is just social networking website, but community website is not just social networking website.
Facebook is a very popular social networking website, and facebook is also a community website. Even facebook and twitter are looks more and more similar now, they are different, you should know they are different not just by their name.
There are many types of community website, like photo sharing, blog, online bookmark, wiki. Social networking is just one of those. Social networking (like facebook and friendster) is a website for users to connect to their friends virtually through Internet, extend their networking through the website.
Other community website serve different purposes, for example twitter. Twitter is for you to share your thoughts (or status) with the others, that's the most common things that people do over there. You might be reading you friend's status or someone who is unknown to you on twitter.
Don't tell me you are a friend of Barack Obama because you know him on twitter. Please don't get it wrong, even is very confusing, twitter is not a social networking website.