social bookmarking

All of these social bookmarking sites, blogs, etc can be fun. However, while they may have a use in libraries now and in the future, I think because of the un-mediated nature, they can also be misleading and ultimately time wasting when they come up in search results. There are many other interesting technologies available, why the extensive focus on social bookmarking? (Yes I wouldn't even look at it if it wasn't required)