Phosphorus and Lime

Still contemplating the problem of form-based web spam. Wondering just now whether there weren't some event based challenges that might thwart spammers. A trivial right-click task, or something like:

copy and paste the animal from this string into the field below:
monday/lion/bank/green


Word categories, terms, and delimiters could be easily randomized -- three chances, impose a time penalty for wrong guesses, reset challenge. You might even color code responses to give a bit of a visual cue to viewers (though this would present a numerical pattern that would be a vulnerability.)

A nuisance even if it works, but a stopgap that, if properly implemented, might qualify as an effective reverse-Turing test and require quasi-AI to break.