Rus - Your question about the definitions of "troll", "lurker", and "SPAM" have all been answered, but I'd like to address a slightly different aspect of your question. You asked what they meant in relation to an unregistered user, and I don't think that was actually discussed. I didn't mean to imply that there's necessarily any connection between those things and being unregistered. I only meant to say that being unregistered makes it easier, under the cover of anonymity to "troll", to use the word as a verb instead of a noun. Many unregistered users, such as yourself, for example, are none of those things. And I don't classify "lurkers" to be of the same ilk as "trolls", in any case. While we always like to encourage "lurkers" to participate, because it broadens the TBN experience, it's not a crime. I go into "lurker" mode myself from time to time because of various reasons - sometimes I'm just too busy to respond in my usual succint, terse style. /w3tcompact/icons/wink.gif Of course, not many here on TBN would classify me as a "lurker" - they just might prefer I was. /w3tcompact/icons/laugh.gif
A "troll" is another matter entirely. Trolls serve no useful purpose in life whatsoever and would be far better off in the same plane of existence as the fairy tale variety - in other words, nonexistent. Their sole purpose in life is to try to stir up controversy of the worst kind - sometimes controversy results in stimulated thinking, but what they try to stir up is just contention and ill will. Some may be simply sophmoric, but most, I suspect, are just losers. I'm not sure if it's a case of "misery loves company", or whether they just find it humorous to start something, but either way, they have no redeeming qualities whatsoever, at least not as it pertains to a forum, newsgroup, mailing list, or whatever other medium of communication they choose in infect.
Trolls are easy to spot, and fortunately extremely rare on TBN. One reason for their rarity is that they don't live long here. (It's a funny thing - I'm not exactly sure what happens to them - their posts just seem to evaporate into thin air...) /w3tcompact/icons/smile.gif
All of which is to say that you are not a troll, nor a lurker, nor do you have anything to do with SPAM. You're just a regular poster who contributes good things to TBN and happens not to be registered. There is not necessarily any connection whatsoever between those things, and I'm not going to bad-mouth lurkers anyway, but the simple fact is that the vast majority of the trolls we have to deal with are unregistered. They don't have to be, of course, but the anonymity makes it easy, as I said earlier.
As for requiring registering causing us to lose valuable posters, let's not forget that the poster gets something from the experience, too. There's something to be said for the satisfaction that comes from being able to help others. That alone is worth the "price" of registering, especially considering that I can't come up with any "price" to it anyway. Not to mention the value of knowledge gained, which is often priceless. And then there's the comeraderie, again priceless. No, I don't think that in a world where "something for nothing" is proverbially impossible to achieve, getting an awful lot for almost nothing is something to complain about.