How unfair that you're expected to sign an NDA on the spot. I'm sure that Amazon and other software companies have spent tens/hundreds of thousands of dollars to protect their IP, yet you don't even get the most basic legal counsel. Why couldn't they mail it out after the phone screening? This almost feels like duress.
You want to interview? Sign an NDA. Otherwise, Amazon is under no obligation whatsoever to offer you an interview. Nothing is being taken from you, because you are not entitled to receive a job interview.
The NDA was very short (I'm not a lawyer, but it didn't seem nearly complicated enough to warrant needing a lawyer to read it) and the recruiters gave us time to look over it. There was nothing ridiculous in it and it was only to cover the interview process.
As far as I remember it was just stuff like "don't share details about what goes on in our interviews with others" which is pretty reasonable.