That already supports a product which proliferates DRM (Kindle). So it's not the best approach if you want to support the DRM-free cause. Plus you can't really purge Kindle of DRM in the system unless you wipe out the whole OS and install something alternative.
That's in theory. In practice Amazon either subsidizes or doesn't have much of a mark up on the price of the Kindles; and hopes to make it up by selling DRM products.
May be. Then it's just symbolic. I.e. buying the product shows support for it in the eyes of Amazon (even if they don't profit from physical devices they benefit from popularity). Not buying it should imply that you want to discourage their insulting and unethical attitude of treating users as criminals by default.
