No, I am not using any of these social bookmarking sites, because I learned my lesson with them.
A friend of mine was was listed in a lot of them and the end of it was, she had to fight against an identification theft. Suddenly she has to prove, who she was and that somebody uses her identity.
So take care, if you subscribe to such a site, some of them sell your data and if you are listed in a few of these sites, people can find out a lot more about you then you really want them to know.