This is something that has been cited on many occasions. The problem (as mostly noted above) is that by doing so you severely limit the usefulness of the Forum as a resource.
A large number of us on the 'cat got our start through posting 'guest' questions, getting answered, and then joining in on conversations from there. It doesn't matter that the only thing that is required is carrying a cookie in the memory of the computer, and giving Max fairly limited personal info. A lot of people either don't believe any level of assurance about that you give them, cannot accept cookies, or otherwise are unable to be members.
Personally, I haven't seen one of the troll threads lately. I've learned to identify where the fuckwits hang out, and don't feed them. Given my druthers, their postings would be prosecuted as what they usually are - verbal assault or hate crimes. Let them rot in prison as a 'consequence' for their idiocy. Unfortunately, that's just really not an option.
M