From mamamusings:
First, it's going to be an enterprise-based tool, that will be
installed and managed on your own server. That's because
centrally-owned and managed social bookmarking tools present a problem
for people working on non-public projects. I was made aware of how much
of a public trail I can leave in my bookmarks when one of my students
knew about my plans to come to Seattle before my department chair
did--all because he'd noticed what I was bookmarking and how I was
tagging it. When I started working here at Microsoft on competitive
projects, I cut way back on my use of del.icio.us, because I was
concerned that I might give away too much of what I was working on to
competitors.