I think that a secondary market for digital works is something that will just never work like it does for physical media, and that's something we just have to accept and move on with.
My biggest worry is that ReDigi is going to end up losing a lawsuit that sets a bad precedent and makes future better technologies impossible.
That said, the RIAA's ownership vs licence vs access debate is BS, and they never even stick to it.
The RIAA needs to change course soon, because unlike the book and movie industries, I can easily imagine a future without a music industry at all.
As for Amazon vs. the authors? I think they are pretty much both wrong, and I'm staying out of it.