Everyone? Or Google? I don't feel particularly happy about being used as a lab rat, so no, thank you - I don't care about the quality of Google's AI. If anything, I would purposefully mislead it if I knew how.
So we will get even more "targeted ads" in our faces? No, thanks. I think ML/AI has a great potential (especially in medicine), but I just don't trust ad companies to use it for any good cause.
Has Google published this training set somewhere? Until they do, you're absolutely right that this is a great way to build a training set, but I don't see how it's to anyone's benefit but Google's.