The new version opens up the bookmarks to be more functional, include tagging, allow sharing of your bookmarks, and includes integration with MyWeb, if you use that service. When you add del.icio.us into the mix, which Yahoo bought some time ago, the company essentially has three social bookmarking products.
My guess is that MyWeb will eventually be merged into Yahoo Bookmarks to create one product, and they’ll leave del.icio.us alone for fear of a user revolt. These social bookmarking services are a great way to share content with very targeted audiences who’ve already identified their interests. This is a very good instructional video by Yahooza that demonstrates Yahoo Bookmark’s features: