Andrew Darby wrote:
> It's anecdotal, but since I added a little "What's two plus two" input
> box to my forms, we hardly get any more form spam.  You could easily
> switch the question each time, although I haven't had the need to.
>
>   
I know that Blojsom, an open source blogging application, has been using 
that kind of cognitive captcha for several years.  I read several blogs 
that are built on top of blojsom and haven't noticed any spam problems 
with any of them.