One of the `silent majority' in a electronic
forum; one who posts occasionally or not at all but is known to
read the group's postings regularly. This term is not pejorative
and indeed is casually used reflexively: "Oh, I'm just lurking."
Often used in `the lurkers', the hypothetical audience for the
group's flamage-emitting regulars. When a lurker speaks up
for the first time, this is called `delurking'.
The creator of the popular science-fiction TV series "Babylon
5" has ties to SF fandom and the hacker culture. In that series,
the use of the term `lurker' for a homeless or displaced person is
a conscious reference to the jargon term.