Bleeping computer...
OK, I think I know why Leeds_Lobber posts as a guest.
It is because he is absent-minded (maybe even as much so as I am) and he forgets to log in and he reads something interesting and he types up a reply and he posts it and...
The bleeped YABB software says "You gotta sign in first" and he remembers that if he backs out and signs in, YABB will consign what he typed to the Great Bit Bucket in the Sky and he will never remember what wondrous words he typed (he's absent-minded like me, remember?) so he just types in his regular moniker but it gets logged as a guest poster.
"How do I know this?" you ask.
BECAUSE THE SAME BLEEPED THING JUST HAPPENED TO ME!!
Alright, yes, if I wasn't absent-minded it wouldn't have happened, it's ME, not the computer ... grumble.