Earlier quoted context omitted.
Good question and I haven't seen a response yet. This may be a serious problem for Amazon since you aren't alone in your blocking of AWS/EC2 IP ranges. If users use the tablet and find that the Silk browser doesn't show them all the sites they want, then people will be disappointed in Amazon. Hopefully they'll separate/segment IPs to prevent users from not using the browser.
More likely, if AWS fails to fetch a page it will fallback on the browser to do the work. So the user will still get to the page they want, and your site will be blamed for being "slow" due to blocking AWS caching.
I think it will only be available via a buried setting that most users will never touch.
Fire seems to discourage any kind of advanced user, it's the king of "no"
Bluetooth? No
HDMI? No
Camera? No
Microphone? No
micro/SD slot? No
GPS? No
3G? No
Android Market? No (only amazon's market)
It also brings yet another browser to worry about for website compatibility and will require simulation to test.