As others have already said, it would scare away the real new users
Some time ago I joined two different forums and my request to become a member had to be approved by a moderator, to make sure I wasn't one of these spammers or spambots who only make one or two posts (usually to advert dodgy merchanises) then disappear off again.
New users should have nothing to fear if they are genuinely interested in the Ship Sim forum and do not have any other hidden agenda. Real guests/users would not be going through every threads and print them all off, do they?
The fact that a guest user are able to access the forum without needing to become a member first, and printing the "Tell us where you are from" thread concerns me greatly - who knows what kind of information contains in that thread? And what will the guest user do with all the stuff he/she has printed off - sell them to marketing/junk mail companies?