First, not everything your app will do is conveniently understandable in terms of resources, just like not everything code does is conveniently understandable in terms of operators. We have, thankfully, largely killed operator overloading and replaced it with functions. Why regress on function naming in our controllers? This is really a paypal_callback, not a PUT on the Paypal "resource", which doesn't even exist and if it did would tie across authentication, billing, and stats subsystems. (What does a PUT on Paypal even mean, anyhow?)
I also get hives when I think about including Rails default routes -- which are programmer-optimized, not user-optimized -- in publicly visible places, where they will get picked up by search engines and seen by copy/pasting users. example.com/categories/1/cards/5 is a part of your user interface... and it sucks. example.com/bingo-cards/holidays/halloween is superior in just about every conceivable way.