If you're involved in creating a social web site, please heed the lessons in The Del.icio.us Lesson, an excellent blog post by Bokardo.  I won't steal his thunder, so you'll want to go read it yourself.  But the teaser is...  He lists 4 solid things to think about when creating a new social networking site.  Things that Del.icio.us does exceedingly well, and the social sites that are failing do NOT do well.  Have a read!