Well, a few months ago I had my go at a service that would use data from people working on machine learning systems so I guess that part is not a big deal. The

Well, a few months ago I had my go at a service that would use data from people working on machine learning systems so I guess that part is not a big deal. The bigger problem is people are accustomed to typical 'write down the word' CAPTCHAs and yet, they're fed up with them, so anything different would only be more annoying and hardly more secure. It's also hard to think of a challenge type that would have enough combinations for blind guessing to be ineffective and not be of the text-based type we all know. You'd need dozens of kitten and puppy pictures in one challenge to have a reasonable failure rate and no one will be interested in solving those.