I'd rather use Amazon than Google or Facebook, but I'd rather use a site that only did identity than any of the rest. (I don't want access to my Kindle books s

I'd rather use Amazon than Google or Facebook, but I'd rather use a site that only did identity than any of the rest. (I don't want access to my Kindle books screwed up because Amazon decided I did something wrong when using them for login, and banned my account. Yes, that reminds me that I need to backup all my Kindle books monthly.) I don't know what the business model for such a site would be, though.