> My noob a-ha example is `rails generate devise:install` where I first thought, wow, what a time saver. Eventually I learned lessons like, perhaps authentication is too important to be hiding from your source code. In fact, maybe almost everything is.

You can view the source code of Devise any time you want on its github repo - it's not hiding anywhere.

I think that having authentication code vetted by 100s, if not 1000s of different developers is much better than rolling your own authentication code.