Yahoo claims 95 million users and 350 million questions asked. That’s a lot of answers, something that would take more than 10 million Dear Abby’s to fulfill.
As a social site, YA offers these social features: add friends to grow your network, invite friends to join Y Answers, send individual questions to friends, vote on other peoples answers, and use the built in IM. Friends on your network, have their questions displayed on your profile page. Do not treat this like Myspace, you want to pick your friends with a modicum of discretion so that you are not in any unforeseen neighborhoods.
SBS has a great writeup about Yahoo! Answers and shows his success as a power question answerer.