The Sims Online:
Social

This is really the only need that requires other people. You could conceivably make your own house and sit there alone meeting all of your other needs, but eventually you'd be miserable because of loneliness. Be sure to get out to other populated homes every once in a while so your social need is met! Just being in a room with others will take care of this one.

The Sims Online Tips, Techniques and Walkthroughs