I am 99.9999999999999999999999% positive the only time you get a facebook nag is if you've signed into your facebook account via your Kindle settings. I've never seen that nag, EVER, and I have finished books while connected to WiFi.
And the popup for rating the book only shows up after you've finished the book, when I usually just press the home button at that point anyway. I don't have a moral objective to seeing the popup
if it doesn't hinder my getting out of the book.
On sideloaded books, this popup is at the 100% (location) mark, on Amazon-loaded books, it is wherever Amazon's algorithms say the end of the book is. Which is very often before end matter, previews, and extra material, like short stories.
Fortunately, I discovered the data is all saved in /documents/{book-title}.sdr/EndActions.data.{ASIN}.asc, so I searched and deleted them all. Since I backup my Kindle for weird reasons, rsync is set to prune out all files containing "EndActions". And a KUAL hack which turns off the popups via the settings database now includes (on my suggestion) a button to "rm /mnt/us/documents/*/EndActions.data.*.asc" for extra security.
This might not suit everybody, but I find it makes for a happy Kindle reading experience. YMMV.
