This was originally a response to an email question I received from a colleague about social bookmarking sites, but it turned into a blog post. While it covers social bookmarking in general, it focuses primarily on del.icio.us for examples:
The advantages of social bookmarking sites over favorites:
1. Web based, so available from any browser and/or computer with web access.
2. Social bookmarks are "tagged" by bookmarkers with appropriate keywords. They can be navigated by tag or searched, so you run into less bookmarking management issues that you may with a traditional directory structure in a browser.
3. Items favorited by more than one person percolate up in popularity, helping you find interesting things to read on subjects that interest you.
An example of this in action is the online account for Technology Evangelist at del.icio.us:
I bookmark things I find interesting and/or potentially interesting to the Technology Evangelist audience into that account using a button on my toolbar. I grab a relevant paragraph from the page I want to bookmark, click the button, then add a few keywords and I'm done. This makes it easy to find things later since I've added both a description and keywords to the bookmark.
Del.icio.us also offers a link publishing service that will automatically push latest bookmarks to our blog as a daily digest. Posts in the links category are generated through Del.icio.us:
This type of linking seems to be more popular with "professional" networks than "social" networks, so social bookmarking is a misleading term. The most bookmarked items on del.icio.us tend to be "How To" items related to technology, blogging, and programming at this point, but that's likely to evolve as bookmarking moves beyond it's techie start. As of today, sharing business insights (well written blog posts on emerging industries, for example) than the latest celebrity news of the day. To get a feel for what people use del.icio.us for, check out their tag cloud of most popular tags here:
Larger font sizes denote categories with more bookmarks.
Social bookmarking fills a unique niche by helping organize truly useful information. It's a bit different from the news of the day content covered by sites like Digg, although there is some overlap. People tend to bookmark content they found useful enough to consider revisiting at another time. This could be content that's simply longer than they have time to absorb when first discovered, but it seems to lean toward particularly well written list of tips, tutorials, or essays on a topics that interest them.
Del.icio.us users can also subscribe to other del.icio.us user's bookmarks. For example, Steve Rubel, an employee of Edelman, blogger at Micropersuasion, and prolific bookmarker on Del.icio.us with over 3000 bookmarks to date, can be found here.
A person could subscribe to his bookmark feed using a program like Bloglines using the RSS link near the bottom of the page.
One limitation of del.icio.us to date is the lack of privacy controls. All bookmarks are visible to everyone else on the system, so this may not be an ideal location to bookmark financial reports of acquisition candidates, the MySpace profiles of prospective employees or other things that may raise an eyebrow. Yahoo has a similar product called MyWeb that does offer the ability to mark bookmarks private, shared with friends, or public, but hasn't taken off like del.icio.us. Yahoo acquired del.icio.us last December, but hasn't done much to merge the two services to date as far as I can tell.
Is web based access to bookmarks the main motivation behind the use of del.icio.us? I don't believe so. I think it's driven more by a form of implied reciprocation where bookmarkers contribute what they've found interesting with the understanding that others will do the same, leading to a community built source of interesting content.