I have a lot of appreciation and even respect for lurkers. For the diffident like me, lurking can be a great way to get to know more about folks with whom you have tangential connections or loose affiliations. It can also be a wonderful way to exercise your intellect by reading and thinking about the many very intelligent things that some of those on the intertubes have to offer. In a professional context, lurking often takes me into realms of discourse where I do not have the inclination to participate but which nonetheless enrich my professional life.
As I respect lurkers, I think that I am a respectful and thoughtful lurker. I try to take what is available for me to observe publicly in the terms in which it is given--to interact when I feel I have something of value to offer, to follow only as closely or as far as I am invited to by anothers' words, images or audio. Above all, I hope that I have never put my thoughts or feelings about those I observer into a space that would intrude on them personally (in place of work, with friends and family, or with anyone else who happens to be lurking) without them having an opportunityto know the source of what I might write or say and to communicate directly with me if they choose.
Clearly the nature of the social web tells us all that my particular view and hoped-for practice of lurking is a highly idealized one that we cannot reasonably believe we will encounter when we put our words, images, or audio out in public. Perhaps the best we can do is to value those who are willing to respect what they encounter of us online--as I hope I do.