I am listening to a talk by Bob Buch, vp of business development at Digg.com. Some of the key points he makes about what makes a successful social media site include:

• focus on sharing – a perfect example of this is Facebook’s Newsfeed
• Integration — build on what exists and works
• get people on your team who grok social media — and have them integrated into your organization; confer to those experts; use their knowledge
• the platform is all about one to many, not one to one; find the influencers, the people who link to lots of people, and get them on board with your story — this audience he refers to as the ‘taste makers.’
• Be authentic — be honest about what your site does and who you are — stick with your core competency; what are you best at? what do people love you for?

Mr Buch focused on Facebook, Twitter and, naturally, Digg.com.

Wired.com, by example, only focused on sharing with sites that their users regularly use. They focus on the top sites that users share to most frequently, and moved the other less-used sites below the main Share feature. Photobucket has done the same thing, with the new Share interface powered by Gigya, which offers the main sites Photobucket users work with most frequently.

An interesting twist on this is to offer a customized experience based on where users are coming from, so if they’re coming from Facebook or Twitter, change the experience based on that source site.

Facebook Connect really helps a site build connectivity and engagement. Any site that requires registration and connectivity can use Facebook Connect to authenticate, and allows an automatic bridge of information between Facebook and a publisher’s site. Additionally, you can use Facebook’s built in user information to target ads and information to that user, and allow a publisher’s content to become syndicated back to the Facebook Newsfeed. Many sites have seen large increases in registration and engagement as a result of using Facebook Connect to log into the site.

I think the key point here is the incredible leverage and network effect that can be gained from building on top of Facebook’s existing network of 175 million registered users.