Is a Kindle usable without an Amazon account ?
So yes, it works just fine without an Amazon account. Granted I bought mine without any expectation to buy ebooks, so I can imagine this being unsatisfying for people the expect to actually purchase DRM books...
It also allows you to tidy up meta-data and stuff to make things look better.
It's definitely a "required" component as far as my Kindle is concerned.
I believe there are legal (non-pirate) ways to buy these, but I've really no idea how good the vendors are or how wide the catalogues are.