Seems to me that there are:

Online folks - These are members who are signed on and set their profile to show when they are online. They may post or not.

Invisable folks - Members who have set their profile to not display when they are signed on. Like me. They also may post or not.

Anonymous folks - People who are either not registered, or are not logged on at the moment. They can't post unless they register and log on.

Normally people think of "lurkers" as people who read and never post. If I don't post for a week, am I now a lurker? If I post once a year, am I lurker? I dunno. I'm not crazy about the word. It sounds so ominous. I think it's more typical that people who lurk are shy about posting, or THINK that they have nothing important to add to the conversation. I'll bet they are wrong!

em