But letting your SO kindle sit in a drawer or on a shelf unused deprives amazon of their special offers revenue just as much as defeating SO and using it on your own wifi. From that perspective, not using your SO kindle is just as bad as disabling SO because it also deprives them of POTENTIAL revenue.
But theft of paid bandwidth by 3G tethering is certainly outright theft because it steals REAL revenue paid by amazon to the 3G service providers.
Morally, there is a world of difference between potential revenue and real revenue. After all, the gazillions of dollars "stolen" from the media moguls with P2P software do not even exist in the pockets of the teenagers that download MP3s and movies, so it is not really "lost" revenue. "Lost" sales that would never have been made anyway is not true theft because it deprives nobody of anything. I have purchased many CDs (I have more than one thousand commercial CDs in my collection) only AFTER I discovered them on a P2P network and liked their previously unfamiar music. P2P certainly functions as free advertising in some cases (at least for those who believe in supporting the creators of their preferred media). I also donate for free software when I find it useful, to encourage more of the same. Monetary karma, if you will...
The point is, be sure to support the creation of more of what you like, and avoid behavior that will make good things go away.
The SO-removal hacks that work on 5.1.2 firmware will be updated to 5.2.0 on the Paperwhite by those who are into that sort of thing.