I just logged in to Facebook, and noticed that Ari Steinberg had just installed the "Google Reader Shared Items" application. Thinking that it would be a nice way to keep my Facebook profile up-to-date with my blog reading habits, I quickly installed it. Then, while configuring the app, I saw it: top shared items!
Scoble is all over it. He calls this feature a Digg-Killer. Is this Scoble being exuberant, or is he on to something? In true MIX spirit, I'll share some numbers and analysis and let you make up your own mind.
Summary: if you use Google Reader, you already can "vote" on stories that you find interesting by clicking "share" to add them to your "shared items list". Now, when you add this application to Facebook, your shared items list is merged with others, so that stories which many people vote for bubble to the top.
Data: Compete.com recently reported that Digg may have more unique users than Facebook -- both around 20 million in a month. Google Reader is the #1 web-based feed reader, according to FeedBurner (not including client readers like IE or NewsGator). According to Kevin Rose of Digg, Digg has approximately 1 million registered users, implying that 95% of Digg's traffic is from non-members. Average time spent per visitor for Facebook and Digg is approximately 12 and 2 minutes, respectively.
Analysis: This feature provides a Digg-like service for anybody who uses both Facebook and Google Reader. These services have large enough user populations to be a significant competitor to Digg. Furthermore, it doesn't depend on blog authors adding "Digg this" style buttons to posts, greasing the skids for adoption. But the biggest potential threat is the integration with Facebook friends list. Currently, when you look at the Digg top stories, you see what is popular with the small number of prolific contributors who dominate Digg -- you don't see a list of stories that are relevant to people like you. Facebook knows who your friends are, so the stories more relevant to people like you can bubble to the top on your list.
If this app sees robust adoption on Facebook, we may see Digg respond. Digg can easily modify their (currently boring) Facebook app to better leverage Facebook. But this would add value to Facebook's social graph and make it less likely that Digg could build up a large independent social graph. Who wants to maintain friends lists in 5 different services? And Digg could easily hook into Google Reader in the same way, though this would give strength to Google Reader, which Steve Rubel last year called a Digg-Killer.