I'm a very occasional guest here, and not much of a user of message boards etc at all, so for me not having registered is, a suppose, a virtual or e-version of a kind of in-person shyness that I've largely conquered in person.
       I should add that I very much appreciate the chance to use the board and to be able to post-so this guest says thanks for the e-hospitality! :)
And another observation--that message boards, to newcomers, whether it's music, macintosh computer or one related to my work, can often seem to be the special territory of those who post often and know each other, know the real names behind the e-monnikers and so forth. Then the outsider or newcomer has a choice--either push a bit to join in with the conversation, or lurk in the background...

As to the points about trolls and unpleasant exchanges--it seems to me that there is a very simple solution, but please pardon me if it's naive or I just don't think like most people. When someone posts something rude, aggressive or provocative, it's only an e-message, they're not shouting at you across a room. What I can't understand is why people take the bait. Silence is a reply too (and might be strong negative reinforcement for trolls