So here goes: A week or two back I was looking for alternatives to CAPTCHA. Keep the CAPTCHA (makes the site look "legit" for the Indian CAPTCHA crackers), and add something that isn't yet standard. Options:
* An extra field that says "What is 2 + 2?" and the user just has to enter 4 in the field.
* An extra field that doesn't use a hardcoded human readable question or equation, but displays it with alternative letters and digits, eg. "What is 2 plus 2?", "What is two + two?", "What is 4 times five?", "What color is a red car?", "Enter the 4rd word of this sentence".
Still thinking on options. Banning the Internet because there are spammers on it isn't an option.