Check out this chart was posted last month to Silicon Alley Insider: Facebook is the most popular platform for sharing content — even surpassing e-mail:

It’s perhaps no surprise, then, that sites like Google Reader have attempted to become more Facebook-like recently, adding the ability to follow friends and “like” links or posts. Delicious also recently made changes in hopes that the site will become a more interactive place for sharing links instead of a repository for storing them.

What also caught my eye was how fractured the social bookmarking sites are. There doesn’t seem to be a truly dominant service among Digg, StumbleUpon, Reddit… all hover in the 3-5 percent range.

With Facebook continuing to grow at a surprising clip, adding users and also buying up the technology and talent of FriendFeed, it’s well on its way to becoming the online content-sharing juggernaut. But while it’s slowly moving away from this direction, most of Facebook’s content sharing still happens behind the wall. It’s tough to do a detailed analysis on what people are saying about content after it’s shared on Facebook. Accessing, aggregating and interpreting that information is the real goldmine for marketers and advertisers.

The chart data comes from Add to Any, which is the toolbar I use on the blog to allow readers to share or save content. It’s one of many similar options blogs and Web sites can use to encourage content-sharing (Share This, TweetMeme, Socialize) so I’m unsure as to how the data would hold up if the study were replicated across all these services.

What are your impressions of the chart? Have you made changes to your organization’s Web site so that users can easily share your content to Facebook? Would the fractured nature of social bookmarking sites deter you from incorporating a bookmarking strategy into your campaigns?