Turing number - for guests when they post

I thought this might be a neat feature, afterall even if you require email address and it that its valid, its easy for Bots or spammers to get around that but using a turing number would prevent that. You could even make it required for registration, perhaps

Incase you dont know what a Turing number is, its when a site has a image with characters and a strange background and the characters are all wierd looking, like some are inflated, others warped or at angles, its like that so Bots and OCR programs cant get around them. The user is required to input those characters in a form and they must match or else the form is not valid.