Richard Heyes has a new post over on his blog covering a possibility to aid in the fight against blog spam - TextualNumbers.

So. What is it? A class (PHP5 only kids) which converts numbers to words. Funky huh? And useful for what exactly? Well, how about preventing blog spam? Allow me to elaborate...

By using this library to convert a random number to its textual representation, you have another method of protecting yourself against automated form submissions. The process goes very much the same (as above) with figlet: Generate a random number, Store it in the session, Generate the textual representation, Print your form, along with an input which the user can use to type the number into, then when validating the form input, match the input from the form against the number stored in the session.

It's not a bad idea, just one more way to do the same kind of thing as before (see Text_CAPTCHA). I do like the suggestion of one of the comments - making questions based on the text/content of the posting, something that could be set by the author at posting time. It wouldn't need to be something difficult, just something humanly-abstract enough that it would be very difficult for a script to mimic it.