If your only argument is "wow, it's easy", you're not arguing from the perspective of any kind of security. I can believe it's easy. But just knowing this does

If your only argument is "wow, it's easy", you're not arguing from the perspective of any kind of security. I can believe it's easy. But just knowing this doesn't give you any understanding of potential downsides. Years ago I lost access to various stack-exchange accounts when Yahoo stopped offering Oauth services. Thankfully not a biggie for me but it soured me on relying on third parties for access to a given account.