1) By using FB, at least initially, they can lower signup friction and get a good bit of social momentum. Especially if users are sharing their "diggs" publicly

1) By using FB, at least initially, they can lower signup friction and get a good bit of social momentum. Especially if users are sharing their "diggs" publicly. Doesn't appeal to hackers, but it works when done tastefully. 2) Discussion on digg was always a bit janky. HN really spoils the idea of social links/comments because they are so high quality here, but when you're targeting the average person, its harder to control quality. Let people sound of on Twitter/FB, and you've created a new marketing vector without directly polluting the experience on your site.