Social bookmarking services allow a user to make
her personal collection of favorite web resources accessible by
the public. The content of this collection can attract users of
“similar minds” and therefore has tremendous potential to
enable networking and collaboration. In this research, we
analyzed a large dataset collected from one of the most popular
social bookmarking services. To understand why there is a
large gap between a user’s explicit network and her implicit
user-user association networks based on common resources or
common tags, we compared a users’ bookmark resources and
tags to those of her explicit network members. Our results
suggest that a typical social bookmarking service user does not
create her explicit network based on common interests. We
discuss the implications behind the gap between a user’s
explicit network and implicit network and propose solutions to
enhance and improve