How about we keep with the intellectual stuff around here, and make 'em answer math captchas. Using latin numerals.
eg, what's LV + IV? Answer has to be given in latin numerals, too.
eg, what's LV + IV? Answer has to be given in latin numerals, too.
We could ask for a basic derivative (for example, of a polynomial), or the value of 'x' in a simple algebraic equation x+5 = 2x + 10
This would probably be very effective at limiting the growth rate of HN, too.