People always come at this from an angle of "what can I do that computers can't?". You need to take into account the incredible diversity of people who use the

People always come at this from an angle of "what can I do that computers can't?". You need to take into account the incredible diversity of people who use the internet, and what they can and can't do. There's already a viral article written by an old lady who can't pass the current captchas. Add to this, people who don't speak english, or don't speak it well; people who battle to read and comprehend text in any language; people who battle with logical reasoning; etc, etc, etc. The lowest common denominator for a task that be easily solved by any human is pretty low.