I think WW has a good point here. There probably are different types of lurking, and it doesn't necessarily involve rudeness. Silence can mean many things. In my experience, most lurkers have been benign. Me thinks there are also various levels of lurking... the person who reads all the mail/posts for a group versus the person who only skims it, looking for threads of interest here and there. Lurking may also take on a different meaning depending on the size of the group.... in large groups, it's expected. In small groups, it may be more awkward.