Stumble Upon - The power of social bookmarking

Have you heard of Stumble Upon? It's a service that "discovers web sites based on your interests, learns what you like and brings you more." There's a toolbar that can be added to Firefox or Internet Explorer. You can mark sites that you like, or don't like. You can tag them with keywords to let others know what they are about. It's also an interesting way to "cruise" the net by clicking "Stumble" and seeing what comes up.

But other than being a fun way to bookmark, review and tag websites, it also appears that sites tagged in StumbleUpon, just list sites tagged in del.icio.us get some extra link benefit in the search engines.

As you probably know, the search engines see each incoming link to your website as a "vote" for your website and the more quality, relevant incoming links your site has, the more "votes" your site gets and the better you can do in the search engines. Now, social bookmarking sites are meant for bookmarking, and not as an SEO tool, but it's an interesting side benefit to note that sites tagged and bookmarked do appear to get some SEO benefit from the incoming links.