I don't know for certain, but I suspect that Google utilized images from the web in training this system. Even if they didn't, suppose they had. I think this can raise an interesting question around copyright.

In training an AI system with hundreds/thousands of bits of data, no single piece of training data makes much of a difference. If one of my images on the web that I had captioned with the keyword 'dog' was used to train this system about what a dog looks like, is the model they end up with a derivative work of my captioned image? Yes, but my data would make up an infinitesimally small part of that model. Yet, in aggregate, the trained model might almost wholly rely on lots of copyrighted, rights-reserved images.

Would the resulting model be a copyright infringement? It would seem as though no rights owner would have a substantial enough claim. Yet, without all of the copyrighted works, perhaps the model would be ineffective.