I haven't heard of social bookmarking before, so this was a new exercise for me. My immediate reaction was one of incredulity. We live in a society where people are increasingly disconnected in person, but we form online communities for everything--and now we even form communities to help each other find websites! Presumably, there is some advantage in finding websites using a social bookmarking site, rather than simply using a search engine. I'm not entirely clear what the advantage would be, except that it eliminates the commercial aspect common to sites like Google and Bing.
In any case, I plunged in and looked around. I searched with tags in my field of study, but didn't find many new sites. I was able to sign in, since I have a Yahoo account, and set up some bookmarks of my own, but honestly, I doubt I will go back to the site. I prefer to use my favorites tab on my browser, rather than having to not only visit, but log in to yet another website.
Aside from sharing information on websites they have found, I don't see much here that would help in the classroom.