Hi, Lydia -
You are correct . . .
none of us ever answered Emily's first question, which was asking the difference between a guest and a lurker. Instead, we answered about the security of the forum and which parts are/are not accessible by guests.
I agree with your definition of a guest, but not necessarily that of a lurker. IMO, a lurker (a harsh term, at that) is someone who has become a member and may/may not post. We have people who have been members here for years, regularly log in and read, and rarely, if ever, make a post. Members still 'hiding', and there is absolutely nothing wrong with that.
On the other hand, I believe that a
troll is someone who is looking for something salacious and is usually disappointed in our forum. Trolls are looking to cause trouble, in one form or another, and once they rear their ugly little heads I'm fairly quick to cut it off and ban them from the forum.
Expanding even further, I think all of us would agree that members who create tales of unbelievable nature, just for their '15 minutes of fame and attention', should be ashamed of themselves. My 'BS detector' usually lights up like the Fourth of July when I see those tales, which belong at FictionMania, and I will question their stories, either in whole or in part.

I'm embarrassed for those members who have bought such unbelievable tales bait, hook, line, and sinker, as it's embarrassing for them
and the forum.
- SL