MYSPACE is an error infested "social networking tool" that high school students use to see who can get the most "friends" added to their page, as other insecure teenagers add them back in order to increase their own friends.

TWITTER is a site for people who think that other people care about what they are doing at any given time; basically the facebook status bar limited to 140 characters, without the rest of facebook.

FACEBOOK is a much cleaner, more private alternative to myspace and is ideally suited to procrastinating, wasting time and stalking old high school boyfriends/girlfriends with their consent.  also a place where people who you never talk to in real life add you so that they will have more friends that they in turn will never talk to.