Twitter = Communicate with new contacts.
Facebook = Socialize with current friends.
In my opinion, Facebook is the new MSN. MSN, and ICQ before it, helped us socialize with our friends. On the flip side, Twitter is a way to find new people who share the same interests as you. it seems that as my friends and I grow more distant, Facebook and I grow more distant. Lately, I have been exploring Twitter more to build a network of business contacts, entrepreneurs, and interesting people.