That's the theory. In practice, your code is clearer if you use Maybe's all along the composition path, otherwise you spend your time unboxing/lifting values.
Finding out at what part of a monadic computation the return of a function put a None when there should have been a Some is much more tricky.
This is where Either comes in handy. Either allows you to attach extra information to the error condition (such as a String). This lets you have the same properties of Maybe but with more information when you need to disambiguate.
