Lots of good cat jokes here. One thought would be to automatically upload the images to Reddit and gather the # of upvotes. The higher the upvotes the more likely it's a cat.
Incorrect. The cat doesn't depend on your validation of its status; if you feed it, you just increase the chance that it thinks you are a subject worthy of its time and attention.
I'm not sure that's a joke. You could upload each pic to both /r/puppies and to /r/kittens, and classify by net upvotes or something. Then you can use the result as training or benchmarking data for a "real" algorithm.
/joke session