Social bookmarking definitely had a heyday before sites like Facebook really took off. The horizon of content consumption began to overwhelm the web audience like we were over-stimulated newborn babies at a shopping mall during the holidays. Our ability to bookmark a website, blog post, news article, photo on Flickr, etc. so we could share it with friends via tags and be able to go back to it later was a great sanity saver for those of us that couldn't possibly read much more in one day.
Digg eventually took the lead as the most popular bookmarking site for awhile, doing celebrity interviews, sponsoring popular events and making sure there was always some kind of "cool factor" present to give you the perception that Digg was much more than a bookmarking site. With tools like Reddit, StumbleUpon and the Guy Kawasaki-backed Alltop, sites like Digg and Delicious took a hit in popularity in my opinion.
In December of last year, there were rumors of Delicious being shutdown by Yahoo, and other rumors that they weren't but were looking for an outside buyer to take them over. Fast-forward to today and you get an official announcement from Yahoo that Delicious has been acquired by Chad Hurley and Steve Chen, the founders of YouTube. Delicious will become part of their new company, AVOS.
I'm not sure what kind of impact this is going to have on the social web, if AVOS will continue to push the Delicious technology/concept or if they're really acquiring it for behavioral data purposes to help build a foundation for a bigger picture project or effort. Time will tell.